There is a very nice Web-based anonymizing proxy here:
http://www.surfola.com.
I use it so that I can post at AnandTech even while using AOL as a provider (yes, I know all about the AOL suckage problem, but my family loves it.)
Unlike most such sites, Surfola does not annoy the user with a bunch of pop-ups, and it is reasonably fast. You can use Surfola as a "guest" for free, and there is nothing to download. They also have a pay service, but I'm happy enough with the free demo that I haven't subscribed.