therealgeorgezimmerman.com looks fake to me. The only confirmation there seems to be is a tweet from the account of Mara Schiavocampo, NBC reporter:

Zimmerman’s attorneys have confirmed the site is operated & authorized by him RT @thinkprogress:@maracamp How do you know this is authentic?

— Mara Schiavocampo (@maracamp) April 9, 2012

But there’s nothing else, and Twitter accounts are often hacked. So I guess I’m saying to wait for a second independent source before you donate.