Mysterious Benedict Society-quirky, fun-different
Possibly some of the Norah McClintock books/series...classic mystery feel, teens solving them, but content should be alright.
Chasing Vermeer-it's middle grade but lots of twists and turns that make you think.
The now classic, View From a Cherry Tree by Willo Davis Roberts

Thanks! I have read Mysterious Benedict Society in 4th grade and I really liked it.

I will defiantly try those suggestions.

I loved the princess bride.

The Westing Game by Ellen Raskin is a YA mystery novel that I continue to love well into adulthood.

The Sweetness at the Bottom of the Pie by Allen Bradley has an excellent oddball young heroine who uses her love of chemistry to solve mysteries and antagonize her older sisters. It's also the beginning of a series (of which 3 have been published thus far) but I've only read this one as of yet.

I also think Arthur Conan Doyle's Sherlock Holmes series is very contemporary and fun and suitable for an advanced 11 year old. The first book is A Study in Scarlet but they can be read in any order. Study is very good and describes how Holmes and Watson first met however there is a middle section that takes place in 19th century Utah that can be flipped through if the mood strikes you.

The Red Blazer Girls (2 books so far)/Michael Beil
The Season/Sarah MacLean
The Hunt for the Seventh/ Christine Morton-Shaw
Found (beginning of a series)/Margaret Peterson Haddix
Haddix has a lot, actually
You should also try Joan Lowery Nixon, she has a ton -- I loved her when I was your age and she's still pretty popular.
If you want something to tingle your spine you could try Lois Duncan -- she's a bit creepier. She's the one that wrote I Know What You Did Last Summer

Thanks everyone!