Archiving video- how do you keep it all organized?

I just started videography and now have thousands of clips that I need to organize and tag. I'm looking for a good program that allows tagging and searching, works with external drives, and can be transferred to another computer when the one I currently have finally bites it. I have a PC, but I'm curious about programs for Mac too.
I've done some online searching, but I can't tell if the programs I've looked at are right for organizing short video clips, since they are all designed for DVD and music collections.
Any suggestions you have would be wonderful, thanks!