Free, Sweet Office Suite. Reads/writes M$ Office, exports PDF, too. Not that you'd WANT to read/write M$ office files, but if someone gave you one, you could open it. OpenDocument is THE STANDARD.
http://www.openoffice.org/
Mozilla Firefox - Unless you LIKE Microsoft's Malware Installation Suite Deluxe (AKA 'Internet Explorer')
http://www.mozilla.com/en-US/firefox/
Subversion/TortoisesSVN - Very competent version control; the second is Windows integration for it.
http://subversion.tigris.org/
http://tortoisesvn.tigris.org/
Perforce is also free and fully functional for individuals and open source projects. It has a 'M$ Office' plugin that works OK for versioning and diffing Microsoft Office documents if you're stuck with that in your organization. It plays nice with Visual Studio, too. I use SVN nowadays.
http://www.perforce.com/index.html
Free Adobe Flex/AIR SDK - In case you want to learn to make Flash content. You don't strictly need Flash. You can for instance import/embed bitmaps and MP3 files and use those in your game. Very adequate for knowledgeable programmers.
http://www.adobe.com/products/flex/
Visual Studio Express - In case you want to build Visual C/C++ projects and whatever their dumb 'flash killer' thing was called. Severely crippled, but useful in some ways.
http://www.microsoft.com/express/
Google Earth - Nifty worldwide mapping doohicky. Can't live without that! No way!
http://earth.google.com/
Foxit PDF Reader (For Windows) - An alternate PDF reader that doesn't suck as much as Adobe's Acrobat Reader, and doesn't have as many exploited security holes.
http://www.foxitsoftware.com/pdf/rd_intro.php
Spybot Search & Destroy - An anti-spyware doohicky
http://www.safer-networking.org/en/index.html
Clonezilla Live - Bootable CD Fully replaces 'Drive Image' or 'Norton Ghost' type software. Even does multiple concurrent drive images over a network.
http://clonezilla.sourceforge.net/
GParted Live - Bootable CD Fully replaces 'Partition Magic', which Symantec bought and destroyed.
http://gparted-livecd.tuxfamily.org/
GMail - Google's Email Service Probably the best spam filtering available, capable of collecting mail from multiple OTHER services and filtering the spam from them for you and presenting you with one 'Inbox' for them all, and though you CAN use your own mail client with it, their web interface works very well. Once you start using it, you'll have no need for a local email client and address book (both very vulnerable to attack if your local machine gets compromised). I can't recommend this highly enough. Everyone I've switched to this has fallen in love with it. One friend got thousands of spam messages a day in her business email, and it went to effectively zero spam messages with no false-positives (that she knows of). Excellent and nearly instant filtering and searching, too.
http://mail.google.com/