I use MacAffee, mostly because I get it free with my service provider. Works well enough, my only complaint being the script blocker that hates my keyboard and won't let you trust a script.
I use F-Secure. I got a free trial from the Microsoft security website and it worked well so when the time came I coughed up for a subscription.
Prior to that, I used Panda for a while. It was great at first, but after a while they brought out a new version of the program which interfered with AutoCAD. It took me a while to figure out what caused the problem, but when I did, bye bye Panda!
We here at the office use F-Secure. The 6.0 version comes with firewall and anti-spyware components. It's not system resource intensive, the firewall is a good one, while the anti-spyware is somewhere between okay and good. Their anti-virus detection, etc. is first rate, however.
Now for my off-topic question: Why when I logged in does the site show me last visiting November 28, 2005?!? I haven't been here for a few weeks, but 2005??? Plus, it shows I have no avatar(?!).
Don't think this has been answered yet. The forum crashed and only an old backup from december could be put to work, so everything between then and may vanished.
I use the Kapersky Security Suite. I used to use Norton and Zone Alarm in tandem, but I have to say that I love Kapersky. Much less resource intensive and works with Windows XP nicely instead of raping it like Norton tends to do. Best money I ever spent. Kapersky AV component will download new anti-virus updates every hour if you want it, keeping your system up to date better than most others who only update their databases once a week like Norton. Stay away from Norton and MacAfee. They are the most popular but also the most resource intensive and intrusive on the market.