Net Hustlin'

Threadless is a clothing company that has on-going design contests. By going to their site you can submit your design and rate other designs. The design with the most votes receives $2,000 and a $500 gift card, and gets sold on the Threadless website. They pick winning designs 4-5 times a year.

They also have a $200 contest for the best shirt slogans. All you have to do is write a shirt slogan and submit it. The competition for the slogans isn't fierce - some of the slogans I saw were pretty awful. If you are clever it should be easy to nuke the competition and win an easy $200.

This is a pretty fun site to peruse because its community oriented. You can rate and comment on each slogan and design, and all designers get their own profile to show off their art work. I come here often because its a contest I actually have a part in.