There is a good article over on Infosec Island by Ashesh Mamidi contributed by fellow blogger Theresa Peyton:
The jist of it, as I've been trying to tell people: Viruses and Malware are NOT just an annoyance anymore. They are a real threat to your financial well being.
Everyone should be running at least a good firewall and an antivirus program. Better yet, I'd recommend trying a software whitelisting program like Faronics Anti-Executable ... if it's not on the approved list it doesn't get run.