Turbo Tax is probably the most user friendly software. In addition there are a lot of website you could file online for free. The IRS website could link you to a site. If you didn't live in Doha for almost a full year you must file taxes. You are only exempt from paying income taxes contingent you made less than approximately $92,000 USD.
If you fall below the minimal income tax bracket for 2011, you might qualify to get some money back provided you have kids, etc.
If your a British citizen, you must file taxes online, but from my understanding they don't check the income you earned and you are exempt from paying taxes.