I've been using this program called
DVD Profiler to keep track of the DVDs I have. It's nice to have an easy to browse catalog, and it's great to print off periodic reports for insurance purposes. Plus there's an ad-supported free version that does pretty much everything you want it to do.
I've had it for a while and dig it, so I registered it for the $30. It's a one-time thing with no upgrade cost, so I figured what the heck - I use it and like it, right?
Registering allows you to upload your DVD collection to their site.
Now you can see which movies I have, and I can make sure I don't run out to Target at lunch and get something I already have. If the family wants to see something, they can look at the list and borrow it from me instead of renting. Pretty cool, if I do say so myself.