You shouldn't pass up giving ReVoice a try on the Shrek DVD. It's a hoot!
It has a large assortment of scenes from the movie and gives you the opportunity to replace any speaking part with your voice.
You view the scene with the original speech, then you get to exercise your vocal chops and perform the dialogue. Once done, you can view the scene with your voice replacement, and save your favourites to hard-disk.
The software does an amazing job of lip synching your voice to the characters, as long as you follow the script, of course.
edit: By the way, you'll naturally need a microphone that you can connect to your computer's soundcard.
Isn't it great how you are able to unlock more fun from DVDs that you already own?
I think we have yet to see a DVD-ROM feature that would really blow you away...though Shrek ReVoice is a heck of a lot of free non-Internet-connected fun.
Here are a couple more suggestions: 'The Matrix' disc has the complete Web site archived as it once stood. Many of the passwords including 'steak' (hinted at right at the end of the movie's credits) work too! These unlock some hidden tidbits such as pictures of the Woman in Red and a low-quality though amusing Matrix Mix comprised of clips from the movie. Of course, the live site has had many more updates since then.
'Lawrence of Arabia' has a slickly designed interactive map.
I don't know, that Phantom Menace text commentary leaves something to be desired, at least in my stupid opinion. You are stuck with a way-to-small movie window that can't be sized and the text itself is not well situated on the screen. I was hoping for something better than the fixed arrangement it left me with. I couldn't even watch it. And the little I did see left me with the impression that it was extremely banal and pedantic beyond all belief. Thoughts of Triumph, the Insult Comic Dog, sprang to mind reading that claptrap.
The DVD-ROM content on the Lawrence of Arabia 2-disc limited edition is the best supplement on the whole disc. It contains lots of information about the actual filming of the movie as well as its historical basis and is arranged by the film's chapters.
The film itself is some secondary color correction and a few audio edits short of perfection, unfortunately.
Here's another interesting, unique, keeping-with-the-spirit-of-the-disc DVD-ROM feature:
Moby's 'Play' (which by the way has plummeted in price last I checked). It includes a program that allows you to easily remix a section of two of his 'Play' hits.