It's probably about time for me to give a plug to some of the software I use frequently, and find incredibly useful.
TextPad is one of the first that comes to mind. A powerful text editor, the features I like most are its support for regular expression search and replace, ease of editing multiple files without locking them, syntax highlighting, and customisable tools to do things like compile your programs automatically.
There's a customised version of Mozilla that I've been trialling at work at the moment. It's called Phoenix, and it seems very good. As in Mozilla, the tabbed browsing is the most obvious benefit for me, but I've found the minimal themes to be good for minimising screen clutter, especially viewing webpages at 1024x768 at work.
Obviously Perl is really useful (I say obviously since this site runs on Perl without a database!), and I constantly find new uses for it.
I've been trying to convince my team about the important of unit testing. Part of this has been installing vbUnit, and getting it working on a couple of small projects of my own. I've also been forced to work with Visual SourceSafe, but that's a far less happy story.
SquirrelMail lets me check my mail both at uni and at mattryall.net, and I'm looking at setting it up at home so I only need to read my mail in one place.