You can choose to create either an animated cinematic trailer or in-game emotes, and the prizes for each category are well worth your time to enter: "Our director will determine which animators shots will be included in the final trailer. There will be approximately 60 final shots in the trailer. The creator of each animated shot chosen by the director to be included in the final trailer will be awarded $500, the inclusion of the animator's shot in the final trailer, a credit in the trailer and a copy of the DC Universe Online game when it ships in accordance with the Official Rules."
The rules for the in-game emote category are similar, except that there will be approximately 42 final shots and the cash prize is $150. DCUO provides a how-to video and the software to create your animations. The competition begins today, and all of the rules, entry information and tools can be found here. Good luck!