Firefox and Thunderbird
I just switched up to Firefox 0.9 and Thunderbird 0.7 and they're really fantastic. I highly encourage switching to Firefox especially.
I keep reading articles about how people should dump Internet Explorer (article 1, article 2, article 3, article 4, ...) and while they all talk about features, defects, bugs, standards support, petty ui issues, and things of that nature, most of them miss the fact that there are still a lot of sites out there that require IE and don't work at all in any of the Gecko-based browsers. Amongst these sites are banks, financial institutions, online stores, and corporate web-sites. While I highly encourage people to make the jump to Firefox, I do understand if you can't because some of the sites you need to access day to day totally suck.