I think we all struggle to keep up with various credentials needed to live our internet lives (single sign on still a dream!) and too often fall back on using the same password over and over again. A few years ago Steve Jones introduced me to Password Safe when he used it to manage credentials we might need across the business (SA, Dell account, etc). It was originally spawned by Bruce Schneier and is now open source. It's a small download, unobstrusive, and has worked for me for quite a while. The only downside I've seen is that it occasionally doesn't get it right when it plugs your credentials into a form (seems to just do username, tab, password) and I've never bothered to try to fix in the cases it fails, just doing 'copy password', pasting, and moving on. It definitely makes it easy/less painful to user stronger/different passwords. The price is right: free!
Lately I've been looking at RoboForm as a possible replacement. It's about $30 and seems to offer a richer experience, but I haven't used enough to know if richer = better.