All the top rated stuff on the main Storygames page is the best place to start, after that, try other stuff by the same authors. Beyond that what you find digging around in the archives is all pretty hit and miss, though there's a few buried gems. Most of the truly dire stuff has been purged.
We sometimes have contests on the forums, and writing prompt threads are popular.
Oh and just fyi, if you imagine Lancelot wearing a comically oversized dunce hat every time you read one of his posts, you'll have a helpful starting point for taking him as seriously as the rest of us do.