Calculate your tax receipt from the US Federal Government based on your income. Find out where your tax dollars are being spent: defense, Social Security, science, health, etc. The app is completely free - search Android Market for "Tax Receipt" by EYMW Soft.
Inspired by the Third Way's report "A Taxpayer Receipt." Numbers differ because this program is more careful about FICA/Medicare accounting. The original can be accessed from this NPR story.