Now regular readers will probably note I'm a bit of a Adobe Lightroom fan. I think its great, not only for managing your workflow, from import through developing to print, but it is also good as a library tool, helping you to catalog and organise all your photos.
However, if you're not quite sure and want to try out some other media managers, then check out the list Techlicious have produced, which includes Picassa, Nero and iBrowser to name a few.
Prior to using Lightroom, there were only two things that came anywhere near what Lightroom does - ACDSee Pro (that they missed - which is a shame because it's better than nearly everything listed there) and iView Media Pro.
I tried all sorts of software to do this and was never happy with anything. iView Media Pro was the best thing I found prior to Lightroom - Lightroom has replicated all of the best bits of iView though and added all of the other lovely stuff like RAW processing too.
Lightroom being this good so early should inspire some good competition though. Microsoft purchased iView which means it should get some polish and they also bought a technology called Seadrragon which looks amazing. If I could browse photos like that in Lightroom I'd be happy!