Dan Wiencek and the folks at McSweeney’s provide some humorous launch pads for your writing. Thirteen Writing Prompts contains such wonderful catalysts as “Write a short scene set at a lake, with trees and shit. Throw some birds in there, too.” Or, if that doesn’t strike your fancy, try to “Write a scene showing a man and a woman arguing over the man’s friendship with a former girlfriend. Do not mention the girlfriend, the man, the woman, or the argument.”
The gang at your workshop will love you for it.