IHateSpam – one of the best commercial anti-spam engines
PopFile Anti-Spam Tool – Free anti-spam software. I have not used it but it is rated as very effective and learns from how you use it
SpamAssassin – free product that works in association with SpamCop to help filter out spam from your e-mail. These are both projects that have been around for a while and have become defacto standards on the Internet
Scambusters – prevent deception, hoaxes, rumours, etc spreading on the Net. Always check it out before forwarding possible hoax e-mails
SpyBot – can detect, remove and prevent spyware of different kinds on your computer – I use it and recommend it (free)
SpyBlaster – prevents spyware from installing, and compliments Spybot
Lavasoft’s Ad-Aware – designed to provide advanced protection from known Data-mining, aggressive advertising, Parasites, Scumware, selected traditional Trojans, Dialers, Malware, Browser hijackers, and tracking components
Mozilla Thunderbird e-mail – free e-mail client that will import all your Outlook e-mail (replaces Outlook). It also allows custom add-ons such as Lightning (a calendar) and Provider for Google Calendar (synchronises with your Google calendar). Thunderbird works on Windows, Mac, or Linux and supports the standard iCalendar format.
Meebo – browser based access to Instant Messengers’s such as Jabber, Google Talk, MSN, ICQ, etc all in one place (bypasses many corporate firewalls)
Pidgin (was called GAIM) – A multi-protocol instant messaging (IM) client. Connects to most of the IM’s from this single program.