VMware - so you can run Linux.
Firefox - less buggy then Safari and snappier too.
Thunderbird - less features then mail, but seems to be stabler.
Songbird - From Mozilla, It's like iTunes, Firefox and last.fm all in one ( it is in beta and still needs a lot of work, but I think it has a ton more potential then iTunes.
VMWare is the only commercial application. Firefox, Thunderbird, and Songbird are all open source, and a lot off people have developed some great plug ins for all 3.