Vistumbler is free opensource software licensed under GPL is a Wireless Access Point scanner for Windows Vista and Windows 7. Vistumbler is a good Security tool for not only to Security Experts but also to users with little technical knowledge to quickly scan and see if there are any potential APs around your place.
Did you know Microsoft gives you free Antivirus/Malware software for personal use? Yes, Microsoft Security Essentials is free Antivirus/Spyware software available for Windows XP, Windows Vista and Windows 7.Micosoft Security Essentials ifor Windows 7 and Vista are available in 32-bit & 64-bit versions as well.
YesScript is a simple Firefox addon which allows you to blacklist websites which will effectively disable javascripts on that website with immediate effect. The addon developer has choosen the opposite path to that of NoScript.
ThreatFire is zero-day malware protection tool from PC Tools which is free for personal use. ThreatFire works alongside your existing Antivirus, Anti-Spyware,Firewall software and employs behaviourial analysis techniques to catch malicous activities on the system like keystroke logging etc.
Tamper Data is a great addon for Firefox browser more for system and network security professionals and network admins and certainly to a degree for network application developers.