Peter Gregory has blogged a list of free security software that is sure to appeal to "ordinary" (as in non-geek) computer users.
The only significant omission that occurs to me is online software security patching. Peter blogged just a week ago about a free and urgent security patch for Skype, perhaps not a good example as he chastises Skype for not publicising the patch. Microsoft Update is probably better.
Personally, I use Secunia's PSI (Personal Software Inspector) to track and stay current with security patches for most of the software on my home system, not just the Microsoft stuff. It does a good job for me but may be too geeky for ordinary mortals. What do you think? Is there a more user friendly option you'd recommend?