From the website:
Illustration Friday is meant to challenge participants creatively. We believe that every person has a little creative bone in their body. Illustration Friday just gives a no-pressure, fun excuse to use it. No clients looking for a particular thing. No one judging the outcome of the work. It's a chance to experiment and explore and play with visual art. Curious about collage? Try it here. Never even picked up a colored pencil? Why not now? Just have time for a doodle? That's okay, we'd love to see it. You don't have to be an illustrator or an artist to participate. Just pick up a pencil, for the love of pete.
I haven't participated yet, in fact I just signed up, but I plan to. Sounds like a great creative release. Be sure to check out all of the great links and work. There is some true talent there.