Our family used them last summer and we're going to sign up again this summer. It's a great way to supply the kids with video games without buying a bunch that's expensive and that they'll beg to use during the school year. Their like netflix so you just send the games back.
Here a contest they're running right now for two free months. Might be worth a try. Otherwise you can sign up for trial membership at
Video Game Rentals: Rent or Buy PS3, PS2, PSP, Xbox 360, Xbox, GameCube, DS, Wii, GBA Games.
contest:
Gamefly.com Videogame Rental Giveaway - Parenting.com