The Security Mentor

Web security expert Jeremiah Grossman uses two completely different browser programs, one for general surfing and another for use with security-critical sites such as his bank. This protects against a whole family of attacks, but not against some of the worst ones.

Other people he knows go further, running their general web surfing in a "virtual machine", a simulated PC that hopefully can't affect the real one. That way even if there's a browser bug that allows a bad web site to take over your computer, it only takes over the simulated one. That's more trouble than you want to go to, but it's not crazy.

Personally I've done OK with the Firefox/NoScript combination on a Mac.