Found out about this one by checking in at the MediaBistro MBToolbox, one of my favorite sites to visit.
The Nation is running a Student Writing Contest. According to the magazine's Web site, they're seeking "original, thoughtful, provocative student voices to tell us what issue is of most concern to their generation." Do that in 800 words (maximum) and submit only one original, unpublished work (work may have been published in a student publication) by March 31.
The winner receives $500 and a magazine subscription; the winning essay will be published in the magazine and featured on the magazine's Web site. Five other finalists will receive $100 each along with magazine subscriptions, and their work will be published online. There's no entry fee indicated, and the contest is open to all high school students and undergraduates at American schools, colleges and universities. For more information and submission instructions, click here.