"700 Sundays" by Billy Crystal!

Bill Bryson's Notes from a Small Island and Notes from a Big Country. He has that knack for delivering a sentence for maximum impact, a sometimes rare talent. Terry Pratchett has a gift for comedy too, any of the Rincewind books would do, or Death. Just bliss to read. You don't laugh with every page but when it hits it hits hard and long.

Bill Bryson's Downunder had me in stitches as did David Sedaris - Me Talk Pretty One Day... Both gave me plenty of belly laughs.

Terry Pratchett - Going Postal. One of his best in my opinion. I love the way Pratchett plays with words, his plots are a very readable mix of the real and the ridiculous and his characters are marvellously real.

The funniest books I have ever read were The Harry Dresden Files; not the stories, just his smart ass attitude about everything.

Between Good Omens (Gaiman, Pratchett) and Douglas Adams's Hitchhiker's Guide to the Galaxy

I agree with Michele G - BIll Bryson's Downunder and David Sedaris. I would add Laurie Notaro.

Meg's response of Going Postal is a good one, but I'm a bit more partial to Guards! Guards! by Pratchett. Really, anything by Terry Pratchett is guaranteed to have me falling out of my chair laughing at some point.

Extremely Loud and Incredibly Close By Jonathan Safran Foer.

Portnoy's Complaint. Not for the faint of heart, but hilarious.

Anything by David Sedaris; have read all of his books and find something to howl about every time.
For fiction, The funeral makers by Cathie pelletier.

This is, of course, an unanswerable question -- but. Joe Queenan's Red Lobster, White Trash, and the Blue Lagoon. Gerald Durrell's My Family and Other Animals. John Kennedy Toole's Confederacy of Dunces. Brian o'Nolan's The Best of Myles. Hunter Thompson's Fear and Loathing in Las Vegas. Roy Blount's Anthology of Southern Humor. Barbara Robinson's The Best Christmas Pageant Ever. Robert Sheckley's Mindswap. The Most of S.J. Perleman. The Portable Dorothy Parker. Robertson Davies's The Papers of Samuel Marchbanks. James Thurber's My Life and Welcome To It.

And so on.

Oh! and Daniel Pinkwater's Young Adult Novel.

The novels of Patrick Dennis: "Auntie Mame", "Around the World with Auntie Mame" and "The Joyous Season" are all available in new trade paperback editions. His books were very popular in the fifties and sixties (and are now all the rage in Italy!). Mr. Dennis left off writing in later years as his popularity waned, and at the end of his life he was serving as butler to Ray Kroc.

'Round Ireland with a Fridge by Tony Hawks. Absolutely great! You will want to go to Ireland and hang out with these people when you're done reading it! I forgot about David Sedaris....good call. And Good Omens by Terry Prachett and Neil Gaimen together is just priceless.

The Milagro Beanfield War. Brilliant and laugh til you annoy other passengers funny.

Fear and Loathing for sure.
I was doubled over on the street laughing uncontrollably.

Cold Comfort Farm probably should be there.

The collected short stories of Ring Lardner. Doesn't matter how many times I read them, they always seem fresh and sparkly.

Franny and Zooey by JD Salinger.

"Strike Two", by Ron Luciano. It's the sequel to "The Umpire Strikes Back", which is also very funny. Baseball fans must read these books!

Apart from the obvious choices of anything by Douglas Adams & Terry Pratchett (both of whom I love to bits!), "The Hippopotamus" by Stephen Fry had me giggling like a silly girl. I do love British humour so...

Also, "The Princess Bride" by William Goldman... I mean, err... S. Morgenstern, of course! :P

"Why my wife thinks I'm an idiiot" by Mike Greenburg; hands down....not even a close second (but maybe one chapter of "Now I can die in peace" by Bill Simmons is in ballpark).

Good Omens by Neil Gaiman and Terry Pratchett, Don't Make a Black Woman Take Off Her Earrings by Tyler Perry

So many of the books above are in my favourite laugh out louds- from Extremely Loud and Incredibly close to David Sedaris' works (ooh, saw him live recently) to the Dresden Files, Terry Pratchett and my ever-beloved The Princess Bride...or my childhood and life long love Gerald Durrell (especially My family and other animals)- aahhhh BOOKS!!

Denis Leary's No Cure For Cancer. ROTFLMAO!!!!!

"A Confederacy of Dunces" by John Kennedy Toole. Helps if you grew up in Louisiana BEFORE the 80's.

PG Wodehouse...I can't believe I didn't include him. His Wooster and Jeeves novels- comic heaven!

David Sedaris, Running with Scissors. I read parts of it to my kids and we were cracking up.

Running with Scissors is by Augusten Burroughs.

oops...I had Sedaris on the brain. Of course, Augusten Burroughs

The Thurber Carnival always makes me laugh out loud!! Or really almost anything by James Thurber.

The Third Policeman by Flann O'Brien

Wishful Drinking by Carrie Fisher. Carrie Fisher has a way of spinning dark realities of her child- and adulthood into something that just struck my funny bone. I think that knowing she wrote the book as a form of therapy help to make the situations okay to laugh at. I laughed a lot. I had to stop reading it in bed because I kept waking my partner up.

"Don't Shoot, It's Just Me" by Bob Hope-not only funny but all the history too.
and "Marley and Me"---I read the book 3 years ago and laughed and cried and laughed and cried.

Hollow Chocolate Bunnies of the Apocalypse, Laurie Notaro's nonfiction books

Dave Barry's "Guide to Guys" by, um, Dave Barry! I can't count the number of copies I've bought of this book, because I keep lending it out and never getting it back. Women AND Men find this book equally hysterical!!

Infinite Jest by David Foster Wallace
Any of Chuck Klosterman's books
Extremely Loud and Incredibly Close by Jonathan Safran Foer
Sounds of the River by Da Chen

"Dave Barry Slept Here: A Sort of History of the United States" by Dave Barry. His version of American history. My brother and I read it out loud together and we were crying from laughing so hard.

Steve Martin wrote a hilarious book back around 1980 called CRUEL SHOES. It is one of the funniest books ever!

The Stupidest Angel by Christopher Moore, closely followed by Lamb.

This Is Where I Leave You by Jonathan Tropper.

I Am Not Sidney Poitier by Percival Everett

Sag Harbor by Colson Whitehead

Me Talk Pretty One Day by David Sedaris

Anything by Jennifer Crusie.

The Santaland Diaries by David Sedaris and The Wee Free Men by Terry Pratchett

a work by P.G. Wodehouse that I read so long ago I've forgotten the title - a sure sign it will come to me upon clicking on "send"....it opens with a teacher giving an organ lesson and the first "hymn" the pupil learns is "Pop Goes the Weasel"

I also nominate David Sedaris. I still laugh thinking of his essay about trying to explain Easter in French to a Muslim woman.

(you should definitely go to one of his book signings if you get the chance, btw. He will personalize every autograph. For mine, he wrote "Vanessa, you DO look like Sinbad." Long story)

The funniest book I've read recently (that is also brilliantly written and sweet in the best sense of the word) is Cannery Row by John Steinbeck.

Here's a random one-- David Sedaris' sister, Amy, wrote a great book on how to entertain: "I Like You." Sort of a cookbook-meet-party-guide, if Martha Stewart were a little nuts. Hilarious and oddly practical. I loved it.

Anything by Dan Jenkins, especially Dead Solid Perfect.
Anything by Patrick Dennis, especially Genius.
Crusade by Greg Crites.

Anything by Jen Lancaster (Bitter is the New Black, Bright Lights Big Ass, etc)

Cooking with Fernet Branca by James Hamilton-Paterson. If you enjoy extremely dry and sarcastic British wit, that is.

Catch-22 by Joseph Heller. It had me in tears and my abs were sore the next day from overuse.

I second Catch-22. My favorite Bill Bryson is his memoir The Life and Times of the Thunderbolt Kid, although A Walk in the Woods is also extremely funny. If you like well researched Regency romance, Georgette Heyer has some very funny reads. Her funniest are probably These Old Shades and The Unknown Ajax.

Hands down it has to be "A Confederacy of Dunces" By John Kennedy Toole. I re-read it every few years and still laugh out loud.

If its laughter you are after Jerome K Jerome is the author to look for.
His classic work is Three Men in a Boat (To Say Nothing of the Dog)

Stephanie Plum series By Janet Evanovich

Ahhh! Thanks for the reminder: P. G. Woodhouse!!

Too bad my favorite book wasn't a book about spelling: Wodehouse is the correct spelling!!

We Are Still Married by Garrison Keillor; The Moon's a Balloon by David Niven.

Anything by Lorrie Moore!!

Catch-22. Also the first couple novels from Janet Evanovich (Stephanie Plum series).

confessions of a shopaholic by sophie kinsella or one for the money by janet evanovich

A Parliament of Whores by P.J. O'Roarke.
No Way to Treat a First Lady; Little Green Men; Thank You for Smoking - all 3 by Christopher Buckley.

I Hate Myself and I Want to Die: The 52 most depressing songs you've ever heard by Tom Reynolds. A total MUST read for musicians, music lovers and song-writers.

Oh, and also Bastards I Have Met by Barry Crump. An encyclopedia of bastards classified by species and given latin names! It's a New Zealand book, and here we use bastard a bit like asshole, not to mean someone born out of wedlock FYI ;-)

"Cooking with Fernet Branca" by James Hamilton-Paterson. I have never laughed so much at a book. Never.

Hated this movie but the book had me laughing so hard I cried - Eat,Pray,Love

Garfield

Christopher Moore always gets me laughing. I just read The Lust Lizard of Melancholy Cove by him and it had me laughing out loud. He knows how to develop really fantastic mental images.

I also agree with everyone stating that David Sedaris gets them laughing. He's also one of my favorites. I really enjoyed Squirrel Seeks Chipmunk!

Hitchhiker's Guide to the Galaxy still does it for me. ;)

The Dresden Files, The Hitchhiker's Guide to the Galaxy, Jeeves and Wooster, The Commitments and The Snapper by Roddy Doyle.