Well now, THAT's a big question.  This can be anything from producing the next big television advertisement for a major cooporation to running through a pudding filled obstacle course to simple dropping a business card in a hat.

Below is a brief list of the major types of sweepstakes and contests:

Blog Giveaways

Cooking Contests

Essay Contests

Food Contests

Idea Contests

Instant Win Contests

Internet Sweepstakes

Makeover Contests

Online Sweepstakes

Photo Contests

Poetry Writing Contests

Recipe Contests

Short Story Competitions

Twitter Contests

Video Contests

Writing Competitions

And that is an abbreviated list.