Flash fiction, or quick fiction, is getting more and more popular. People lead busy lives, and it's hard to sit down with a thousand page novel and spend the time to really get immersed in it. You can read a flash fiction story, however, in about the time it takes to brew a cup of coffee. Flash fiction is by definition short: these stories are always less than a thousand words, sometimes much less. Writing it is a lot quicker than writing a novel, too, which may be why more and more writers are turning to flash fiction. You can write the first draft of a flash fiction story, edit it, and send it out to an online magazine in a matter of hours. Where are these magazines? Just go to: Flash Fiction Markets: A Collection of Websites and Magazines That Publish Micro-Fiction
This site has a listing of flash fiction markets, and if you scroll to the bottom of the page you'll see more magazines listed in the comments section. There are lots of other markets out there, but this is a good starting place to see where you can submit your stories.