Skype is another killer-app for the modern personal computer. If you haven’t already heard of it and installed it, go get it. It’s the first and one of the few VoIP applications on the market that "just works".
Paint.NET is just a nice free replacement for Windows Paint. It requires .Net Framework 2.0 but that’s included in Windows Vista. For a managed programming language, it’s not that bloated and loads relatively quickly.
If you don’t have a Nero for your CD or DVD burner or some other burner application, Infra recorder is a good free alternative. Not only that, it’s a lot less bloated and it has a small memory foot print.
For anyone who wants to take their movies on the go or backup their DVDs to a smaller format, Dr. Divx is an excellent free solution. Unlike the commercial Divx encoder (which I bought and can’t use), Dr. Divx actually works in Windows Vista.
If you are the kind of person who likes to download videos (especially from questionable sources promising adult content) and you don’t want to end up with malware, K-Lite Mega Codec pack plus QuickTime Alternative is for you. This is CRITICAL security advice that everyone needs to know about.
As good as the built in CAB and ZIP utility is in Windows XP and Vista, it isn’t enough because you need compatibility with all the other compression formats out there. IZArc will open any compression format under the sun and it’s free, unlike a lot of other utilities on the Internet.
For me, the only good anti-virus application is no anti-virus -- but I realize that most consumers need some kind of protection from the hostile Internet and often themselves. So a really nice compromise is AVG Antivirus Free Edition which has a really small footprint and doesn’t slow your computer down to the point where your dual-core PC feels like an 80286 computer circa 1982.