“24 Hour Comics,” started by Scott McCloud in 1990, will be held in NYC this weekend. Here's the definition for this unique event from the official website, http://24hcd.blogspot.com, “24-Hour Comics Day is an event held around the world which challenges writers and artists to create a full 24-page comic in 24 consecutive hours. Thousands of artists take the 24-Hour Comics Day Challenge every year!”
This is a great exercise as you're not paying too much attention to the quality of the comics, but you're just getting some story and drawing done!