Drupal is good. If you like it, you might also want to take a peek at CivicSpace which is built on the Drupal platform and is aimed more at activism, but it does have a US zipcode database you can download.
I have also experimented with Mambo, and been impressed with its flexability.
All of these are OS (which is a plus in my book), but most only come with a few default templates. If you want to avoid the “cookie cutter” look you’ll have to be familiar with PHP and CSS to design/modify your own custom template (or be willing to pay someone to do so).