ChrisJoice.co.uk

For both my own reference and potential use for other people, recommended software. Because sometimes free stuff is worth more than the expensive stuff.

Anti-Virus.

avast! 4 Home Edition
Free for home & non-commercial use. Requires registration (free) which needs to be renewed. (Windows)
On access scanning, automatic updates, good virus detection.

AVG Free Edition
Free for home & non-commercial use. (Windows)
On access scanning, automatic updates, good virus detection, been around for ages.

Firewall.

ZoneAlarm Free Edition.
Free for home / non-commercial / charitable use. (Windows)
Simple to setup and effective, per application control.

Malware/Spyware.

Lavasoft Adaware 2007 Free.
Free for personal Home use. (Windows)
Oldest and best. Simple to use.

Office/Productivity.

OpenOffice.org
GNU GPL. (Windows,GNU/Linux, OSX, BSD etc.)
In some ways better than other more expensive suites, in others just equal. Uses open standards.

Image Manipulation / Photographic postprocessing.

The Gimp. (The GNU Image Manipulation Program)
GNU GPL. (GNU/Linux, Windows etc.)
Probably the best graphics program I've used.

Web Browser.

Firefox. 
Mozilla Public License. (GNU/Linux, Windows, OSX, etc.)
Ace browser, very standards compliant, best extendabilty of any browser.

Opera.
Freeware. (GNU/Linux, Windows, OSX, Mobiles, etc. etc.)
More secure than Firefox technically speaking and better rendering engine. Also has mail and bittorent clients built in. Versions are also available for mobile phones etc.

E-mail Client.

Thunderbird.
MPL. (GNU/Linux, Windows, OSX etc.)
Can cope with pretty much any kind of account, but can’t minimize to tray.

Evolution
Open Source (Linux, anywhere the Gnome desktop runs)
Very fully featured E-mail client, has GPG built in, Calendars, Tasks, etc. Similar to MS Outlook. Also can’t minimize to tray. I use Alltray for that.

Instant Messaging.

Pidgin.
GNU GPL. (GNU/Linux, Windows)
Simply the best out there for any platform.

Operating System.

 Arch Linux.
GNU GPL, unless you install something which isn’t.
Fast, simple, but not for the unsure.

Sabayon Linux. 
Mostly GNU GPL, some proprietary which can be removed.
Fully featured, maybe a little too much so but the best out there for out of the box.