There is a free Bitdefender version with positive reviews, you can check it out at
http://www.bitdefender.com/solutions/free.htmlI never used it so can't say whether it's really good or not, but I will give it a try since I have to install an AV product for my family PC.
Through the years, I have used a combo of Kaspersky Antivirus + Comodo Firewall with IPS protection, and it worked for me, but it's true that Kaspersky is a resource eater, and you have to tweak things a bit if you want to use a combination effectively.
For web protection, Malwarebytes Pro offers that, although I've found it annoying and prone to false positives on some sites. I think a combination of addons like NoScript and common sense when browsing would be more useful than a security suite for web surfing.
There is also an anti-spyware program called Spybot Search and Destroy that performs what they call immunization on browsers to block malware infected sites, but the program is another resource hog, and I can't say how beneficial it really is. And as an aide, when I did a routine port scan against my system with Spybot installed, I discovered some of its services were listening for who knows what.
Just keep in mind that the antivirus solutions are far from perfect and could actually be used against your system. There was a very interesting paper I read about attacking AV programs that you can find here:
http://mincore.c9x.org/breaking_av_software.pdf
