I've been playing a fair bit of Minecraft on the xbox since my youngest got it after christmas, It's a great time killer and really does show how sandbox gaming works. Exploring creepy caves full of monsters and tryign to get out alive with the iron ore and coal you need to get a good suit of armor made so you can explore wider and build a cool castle (or whatever lese you wish) is about as sand box as you can get.
I've been playing this alone, i know it's possible to play online, but I'm having fun being a noob and don't need to have more experienced players ruining the fun of discovery for me even if I do find myself asking my 6-year old how a certain doo-dad works in the game. I'm sure i'm lacking some of the fuller experience by interacting with other people but it's fun having no one lese kick over my sand castles at this point.
There's a lot of lessons in Minecraft for what could work in a sandbox setting for an RPG and that is certainly coming up in a future post but now I have to go get some wool to build a bed so I can have a safe place to sleep a few mountains over.