User-agent: Mozilla Thunderbird 0.7.1 (X11/20040626)
SwitchProxy lets you manage and switch between *multiple proxy
configurations* quickly and easily. You can also use it as an anonymizer
to protect your computer from prying eyes.
Main bummer about that is it's a global setting. I wish I could control
the proxy settings per TAB, not globally -- since if you've got Hotmail
(or whatever) open when you switch, you've just advertised your identity
associated with your new (tor) IP address.
Remember to close everything before you switch (and turn on the option
to clear cookies in SwitchProxy).