I've used TOR. It's pretty nifty, and if you're feeling paranoid about your privacy, it's not a bad way to go. I wound up uninstalling it, however, since the Vidalia package I downloaded ran persistently. I mean, of course I could turn it off in msconfig, but still. I just don't need to be anonymous online more than once a month, when I check out the blogs of old acquaintances and don't want them to know I was lookin'.
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If you pair Vidalia with TorButton, you can toggle TOR on and off while your browse in Firefox. Kinda nifty.
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Of course, there are downsides to anything ...
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