You can do some amazing things with Excel if you really get into it. Most people only use about 10% of it's functionality I'd guess.
I do not like putting my list of games online. Why wait for it? I believe Game Collector is the best option though hardly perfect. They are beginning to make some progress again on adding games automatically (it was cooler when AllGameGuide.com allowed them access).
If you only add a couple games at a time (after you've entered your collection) it's great. You'll need to steal cover scans and such from the sites already discussed, but does not take long if you keep up with it. (OK, I'm wayyy behind in updating myself...)
Later,
Trebuken