|I have used Avast on quite a few machines.|
My preference at home is Webroot, but it is one you will need to pay for, though they do have a nice discount for 3 or 5 machines.
Right now though, there is a 100% rebate through NewEgg.com:
for the 5 machines complete version (presumably for new customers, presumably for the first year). Here is their site:
I concur, stay away from Norton. It is a system hog and is not anywhere as good as their hype is. They are just good at convincing people that it is good. If you want completely free, go with Avast Free Version, you only need to register it to keep it free for personal use.
You have to be a little bit crazy to keep you from going insane.