A simple tutorial made by a friend about how to use masking in Sony Vegas.
Combine this with keyframes and you can do loads of things. There's a simple example of this in one of my movies at the beginning. The 3 tanks are all me and you can see the right 2 fade out near the end.
[media]http://www.vimeo.com/1094787[/media]

This image isn't showing up at the right resolution so just right-click and view image in new tab.

[media]http://www.blueentertainment.net/images/masking.jpg[/media]