And if so, how does it work and what kind of trade-in value can I expect? I have a lot of DVD's and XBOX 360 games that have no other use to me except for capturing dust.

How much? With Moviestop it sounds like a buck is pretty much the average. If I can get around $5 I'll be pleased.

I recently used gazelle.com and sellgamesonline.com and i got more than i expected. Gazelle updates you quite often the other site doesnt, you have to call them to keep track of your package and the site doesnt look all that trusthworty but they actually are.

Depends on how new the game is. If more than a year, you will get about $7 or less. If new, you will get between $10-25. I got $22 for Red Dead Redemption. Usually they will give you about 10% more if you use the trade-in-credit to purchase a used game from the store.

Here is the value of my recently traded in games from 9/30:
Halo 3: $4.80.
Borderlands: $10.80
Halo ODST: $7.20.
Crackdown: $3
Battlefield Bad Company 2: $14.40
Left 4 Dead 2: $9.60
The Orange Box: $7.20
Red Dead Redemption: $21.60