I originally wrote this as a comment on this article, but it seemed like it was worth doing a hackerspace post.

1. Use H&R Block’s online filing software.
2. They will offer to pay you a 10% bonus (5% if you use one of their more basic programs) if you elect to receive part of your refund in gift cards.
3. Choose a store where you can buy things you would buy anyway, and replace your budget for those things with the gift cards. Otherwise you’re falling into the trap of treating your refund as a windfall.
4. Get enough gift cards that the 10% back cancels out what you paid to file. Or take a step past that and make money on the deal.

Et voila! You just filed your taxes for free (or better) with a very reputable company that offers guarantees, audit support, and a convenient interface.

More information at their site here.