"At a Wi-Fi hotspot, you may need the security and anonymity of Tor, but on a secure network, the higher bandwidth of a direct connection becomes more important. Torbutton is a plugin for Mozilla Firefox that enables users to easily and rapidly switch Tor on and off.
"Torbutton works by flipping the browser's proxy settings back and forth between a secure, 'Torified' setting and the unsecured default..."
