End the corn subsidy, repeal the patriot act, track what your senators are doing for causes you dis/agree with.
I’ve been maintaining a website with the goal of ending the US Corn Subsidy (both of them, yes we have two different kinds), you can check it out at endcornsubsidy.wordpress.com. One of the biggest issues I have had is making it easy to show people who (as in a senator or representative) they should contact. There is currently a bill in the senate that would end the ethanol subsidy and tariff which is a good first step, check out the link for more details.
OpenCongress.org is an open source website basically designed to help open up Congress! And they are trying to eventually help open up state and even local level government. How does it work? It let’s you track what your senators/reps are actually doing, and find and track how legislation you are interested is doing. So much of what happens in government never makes the news, this let’s you have a much better idea what’s going on.
They use a lot of really cool open source technology and have that as a philosophy that it must be free software. They welcome involvement and contributions.