I saw Business Card Fiction being talked about a while back, and added it to my RSS feed as I loved the idea of it... and I'd forget about it otherwise. Instead of a word count, you're limited by space. To some degree you can tweak it, based on what font you use (and I am a sucker for sexy fonts - though most of them are pretty illegible if you go too small). My story wouldn't fit landscape, but there was buckets of space left over when it was portrait. For the inaugural prompt, we had this lovely scene:

And after talking about how I love fonts, what did I end up running with? Times New Roman