Assalam Walaikum,
I suppose using a Muslim face book might get a bit  difficult, because you have to add, salaam, ins ha Allah, Masha Allah, etc in whatever you speak,hope for or wish. And it's a bit ...lonely speaking in there.since if you have friends who r also non Muslims,they cant join that site. I prefer using the original face book,since almost everyone knows that site. No offence, but good effort,you can talk and be friends with good Muslims.

I did have a muxlim account-but back then it was called muslimspace.com
They must've changed the name.
@Werty- Saying inshallah, mashallah etc shouldnt be too hard to say if your friends are muslim. And now they have abbreviated ways of saying the "islamic phrases"-ask me if it is 'correct' or not, I do not know!
And joining an islamic 'facebook or myspace' is in order to make friends with other muslims, and surround yourselves with them, I would prefer to do that than be on facebook with no muslim friends. But our likes and dislikes may be different...
But all I wanted to say @ Seamar is-I think it is a wonderful idea to have such a site, where muslims can populate it and make it just as popular as facebook and myspace!!!

I really like http://mymuslimbook.com its has some exciting features and the owner is soon is gonna make it even  better.It has over 500 members and growing everyday.