Recommended Software

Blender - For 3D modelling and animation.
GIMP - GNU Image Manipulation Program. Download for Windows and Download for Mac OS X.
Firefox - Arguably the best web browser available, for a number of reasons including performance, standards support and security. The best feature though is the plug-in support, after a while they become hard to live without. For example, Adblock Plus, Download Statusbar, NoScript, PDF Download and Video DownloadHelper.
Inkscape - A vector graphics editor.
iTunes - Many pieces of software play mp3 files, few make tagging and organising them as easy as iTunes.
OpenOffice.org - Word Processor, SpreadSheet, Presentation and DataBase software.
VLC Media Player - A media player that will play just about any video format.

7-Zip - Archives and unarchives file from and to a number of formats including ZIP and RAR.
AVG Anti-Virus Free Edition - Free anti-virus software, just make sure you are downloading the free version. There website is designed to confuse you into paying for stuff you don't need.
IfranView - Image file viewer.
JkDefrag - Big improvement over the defragger included with Windows XP. See also PageDefrag which defragments special files that other defraggers can't touch.
Notepad++ - Text editor.
PuTTY - SSH client
Windows Search - Creates indexes of the files on your computer, so searching for files is a lot quicker.

Growl - A service that lets applications post short notes to the screen.
NetNewsWire - News feed reader.
Perian - Adds the components that QuickTime needs to play a range of common video formats.
TextWrangler - Text editor.
Windows Media Components for QuickTime - Adds the components that QuickTime needs to play Windows Media formatted media files.