I don't know of any others either other than mediums such as this forum. Forums on their own are clunky though when it comes to trying to connect with other gamers and finding guilds. I checked out the link you posted and it seems interesting. I personally don't want to use Facebook either because I'd like my personal and gaming lives to remain separate until and when I decide otherwise. Guild keep site seems to have a lot of potential. I've signed up to see where it goes.