I try to post as many filmmaking/video contests that are available online – but this site – Online Video Contests – has ‘em all!
We are a resource for filmmakers, directors, animators, and amateur video enthusiasts to easily find (and win) video contests. – from onlinevideocontests.com/about
You can search and sort the types of contest that best fit your interest/needs from their easy-to-use “find contests” tab. They are currently running 165 total contests, with a cash value of $660,903. Check it out!