Thanks to the post about OpenDataPhilly, I actually found out Tucson has a similar website (or at least the initiative. It didn't look like there was much on the website yet.)
Supposedly the minutes of all meeting conducted in Tucson are available online at the government website, although I have yet to look for any. Either way, it is a good step towards keeping things transparent.
We have the Census Bureau for lots and lots of population and demographic statistics. There is also city-data.com, which has a lot of information, albeit some of it inaccurate.
One of the best things about city-data is actually the ability to interact with others about the city in question.
It doesn't seem like the open data movement has fully taken hold here yet. One effort to make data more open in the US is the Code for America project.