I don't know if you've seen this going around but a lot of people are doing it: It's the 30 Day Drawing Challenge, in which there is this list and each day you have a different topic and you try to reach 30 drawings in 30 days without skipping a day. From what I could find out researching on google it started with the initiative of Sylvia Tran and it turned viral on tumblr and other social networks. I found out through people reblogging this version of the challenge by Allison Lehman.
Here's the list of topics by day:
Anyways, it's pretty fun and a good excuse to flex the drawish muscles and stuff. You can see some of the art that's being done so far by following the hashtag #30DayDrawingChallenge on twitter or the tag "30DayDrawingChallenge" on Tumblr.
Here's some of what I've done (click to go to the Tumblr tag filter):