What plugin or method do you use for allow for...

Hi:

What plugin or method do you use for setting up to allow users (multisite compatible if possible) to login or register using facebook or twitter? For example on the wpmudev.com site etc?

What solutions do you use?
If it is custom, what plugins for ms do you recommend that would do the same (I would like them to be able to login regular without facebook/twitter or with f/t too)?

Thanks...

Greg