Today, Wizards announced that they're holding a contest, where entrants design decklists for a set of online duel decks based off Mirrodin Pure and New Phyrexia.
They also happen to be giving out a good chunk of product for the victor, so fire up that gatherer search tool and get building! You can rest assured that I've already submitted my entry, and anyone with a few hours to kill should give it a go as well. The announcement, with links for full rules and where to submit your list(s), can be found here. Note that you DO need to be eighteen to enter, since you need to be able to consent to handing over the IP rights to your submitted content.