Keeping track of what you watch

[Crispy0009]

How do you guys keep track of what you've already watched?

For example: I have almost 600 blu-rays & nearly 1400 dvds.
I've already watched the feature film, but I can't remember if I've listened to the commentary track or not. Or, have I watched all of these special features & deleted scenes?

I'm wondering how some of you keep track of things like this or do you just have great memories?