I've been using Avast! ever since version 4 and am very satisfied. It's gotten better and better over time.
I just watched a tech program on CNET that said all you need is one good anti-malware suite rather than having several different anti-malware programs such as an anti-virus program, a firewall program, etc.
So does Avast! Free perform all the security functions that a firewall program such as ZoneAlarm, Comodo, Outpost, etc. do, or should I run both Avast! Free and a firewall program such as ZoneAlarm?