I normally use AVG Anti-Virus Free Edition and recently bought AVG Internet Security, their commercial version of the free edition.
I like it very much; it's light on computer resources and saves my rear-end on a daily basis.
I've had numereous pop-ups of AVG reporting that it prevented injection of malicious Javascript hidden in webpages, just during browsing.
Awesome product that I wholeheartedly recommend to anyone.
--Sillyputty