Freeware
Quicklook plugin to colour code program files
Unicode checker which allows you to view all sorts of info on Unicode characters
MT Newswatcher is a great program for viewing newsgroups.
Camino yet another browser, but this one seems very fast.
Textwrangler is another text editor, but the feature I like most about it is that it can open & edit files from an ftp site
Not Freeware
Textmate is a very feature rich text editor that I use around 1% of.
Omnigraffle - used for creating all of my diagrams for lecture notes
Warp - makes using spaces better by allowing you to "push" to a new screen.