I've been writing stories all my life. The constraints of writing prompts have been the greatest source of inspiration. Of all the writing prompts resources I've used, CreativeCopyChallenge was my favorite.
I participated for 500 consecutive entries! during that span, I created one novelette, a Halloween collection, many shorter serials, poetry, rants and serious essays. Many of the entries have been polished and reposted here. You can browse the tag cloud to get an idea of the variety of subjects you'll find.