I saw a commercial for this on TV, it looks interesting:

http://www.freeturbotax.com

"If you have a simple tax return, TurboTax Free Edition is the easy way to do your taxes and get your maximum tax refund."

The free edition is brought to you by the same company which makes the paid version of the software, so it is legitimate. It should be noted that only the federal version is free, the state version is additional.