As well as my own Editorial Cartoon Caption Contest (still time to enter), there are several friends around the net that are also doing contests.

Jill at Elemental My Dear is holding a contest all month long encouraging readers to use to their own blog to “submit a post that reflects the saying “April Showers Bring May Flowers” in any format you may like such as…photography, poetry, short story, cartoon, etc.” She will link to your posting and give away 3 5×7 photos.
Ken at Rick the Stick is encouraging readers to come up with creative ways to promote his webcomic. I tried my hand at a theme song for Ken (we’ll have to wait and see if Ken ever lets it make the light of day as I need Britney Spears engineer to make me sound good). Contest goes through the 25th of this month and the winner will be tooned as a guest star in the strip.
Samantha of Life’s a Witch is having a one week contest to win copies of her comic collections. Every tweet or comment on her site will earn you easy entries.
Finally, not a contest but Nate is looking for guest cartoonists to take on his adorable characters from Knocking on Heavens Door as Fan Art. I have to clean up my act before I can figure out what to submit.