Being a Firebird fan, it's already installed. You have to work a bit at this browser to get it to behave as you'd wish it to. However, once it's up and running it's the best Browser around in my opinion.
Also just released by Mozilla:
The latest version of their browsing, e-mail and editing suite (this is now up to version 1.5).
Mozilla Thunderbird 0.3, a very good stand-alone e-mail program, which uses Bayesian SPAM filtering (described in an earlier thread).
The above programs are under constant development but the 'milestone' releases work very well. Don't let Harish and I be the only ones to discover the benefits of Mozilla (well ...and Sue because she uses Netscape, which is Mozilla based

) Give them a try. They are all free and work quite happily alongside Microsoft products.
Read about them
here