I absolulely love My Movies as I have been using them around or over 10 years and their desktop application is free and lets you keep track of all your stuff.
After many many years of getting good use from this app, I finally decided to pay for their mobile app, which is around $8, and it's well worth it as you can do all you can do from the desktop app on it with the added convenience.
They even give you a free website to host your collection that you can access wherever there is an internet connection. Here's mine: http://c.mymovies.dk/superfist/group:owned