Student Art Guide is a GREAT source for sketchbook/project/concentration topic ideas.  Make sure and explore the 'Articles' and 'Resources' areas.
The Official CollegeBoard AP site.  Dig around and find sample student portfolios with scoring rationales, course overviews, and course info regarding AP 2D Studio Design
Web aggregator Colossal combs the internet for interesting stuff.  It's a good place to browse when you're bored or looking for inspiration.
Newbury Park High School has TONS of sample student photography portfolios (with scores!)
Concentration Idea Lists... You know how to Google things.  Have you tried Googling up some ideas for Concentration topics?  There are a lot of examples out there- Here's a good one.  And here's another good one.  
Like Visual News, another aggregator site to explore when you need a hit of inspiration.
(literally) Everything is here.  
A massive archive of searchable artworks by pretty much every artist ever.
All kinds of sample portfolios for past years' AP 2D Studio Design students
Examples provided by CollegeBoard
Interactive visualization of how different camera settings affect overall image... Do you know how changing settings (Shutter speed, aperture, ISO, etc) affect exposure, depth of field, focus, and grain texture?  This site will help you understand those relationships and better control them in your own work.