Wow.... Where is sooo much good freeware out there! Here's a few that I use every day:
Mozilla <-- You should know what this is already
The Google Toolbar <-- If you're not using Mozilla, you should at least use this with IE.
PuTTY <-- Telnet client with SSL encryption
RealVNC (Or TightVNC) <-- Free remote desktop control software
UltimateZip <-- Supports more formats than WinZip, and it's free without a nag screen!
3DMark2001/2003 SE <--- Ok, so it's not the greatest benchmark in the world, but it still LOOKS pretty

OpenOffice.org <-- It supports most Microsoft Office file formats, and allows you to save as a .PDF file!
Convert 4.1 <-- It can convert pretty much any measurement unit in existance.