I know Sony Vegas has chroma keying (a.k.a. green screen). I used it to make a music video for my daughter last summer. Ulead's VideoStudio also has good chroma key support. It's easier to use than Vegas. But, Vegas gives you more control over the settings. Tip - make sure you don't have any excess shadows in your shots. Also make sure the green (or blue) cloth you use has no wrinkles or folds. They are hard to key out. In other words, have good lighting in your shots.
The trick is to take the blue/green screen out, and a lot of programs do it by just eliminating the color (hence, "chroma" keying, chroma being an old greek word meaning "color") but there is a better way called vector keying, which basically takes a snapshot of the entire background and eliminates it, which is the ultra software from seriousmagic.com They were the bomb, and I use ultra 2 and it works great, but a few months ago were bought by a big company, so we'll see if it remains great. But for taking out the green/blue screen, its the best