Security related (software) AVG (Antivirus) Totally free virus killer thats seems to do as well as Norton etc, auto updates.
  Spybot Search + Destroy A good, free (donation-ware) spy/ad bot /keylogger finder. After a clean install including my usual software I had 3 ad bots so I have some interfered with install files. Always try and use the main download and not the smaller mirrors or other sites not linked to from the software homepage. Needs updating weekly.
  Spyware Blaster Active X and script protection, working on the prevention better than cure idea. Protects the registry, is not running all the time.Works in conjunction with Spybot S+D offering all round protection. Donation-ware). Needs updating weekly.
Security related (online tools) Samspade's Tools Everything from WHOIS to Traceroute
  VisualRoute Server  Detailed tracing (with on-map routing shown) with PINGs and error checking (registering now required)
Browsers Firefox Tabbed browsing (nicked by IE7), live (RSS fed) bookmark buttons, less security holes. Great skins and plug-ins (Adblock/ Flashblock). Seems to crash more than Mozilla suite (netscape mod) but supported against the latest threats.
Software sources Oldversion Essential for getting old versions of software eg. Zonealarm or Getright without ads or new annoying features. Clean downloads (so far).
File conversion PDF converter The old way of converting to PDF was producing illegible documents (newer isn't necessarily better), this works nicely.
Others    

Accurate on: 11/08/06