There are plenty of ways to utilize the Tor network for a little added browsing privacy - like OperaTor, for example.If you'd prefer a single anonymity solution that can handle any browser, portable or not, give PortableTor a try.
It's Tor, Vidalia (a GUI frontend for Tor), and Privoxy in a single, portable package. All you need to do is launch PortableTor and edit your browser's proxy settings to point at 127.0.0.1:8118 (the port can be changed).
Even if you're not going to run it from a USB flash drive, this is still an uncomplicated way to anonymize your desktop browsing as well. All three apps use a combined total of about 26mb of memory, the bulk of which is consumed by Vidalia.
The Sourceforge project page also list several Firefox addons that you may want to add for extra browsing security, like NoScript and No-Referrer.
PortableTor is a free download for Windows only.
