How to make advanced login system

Hey guys, how do i make a advanced login system in wordpress. Like I have a site with many subdomains and some of the subdomains are running on wordpress. I want one login server to be used by all of them as it would make it easier for the visitor. I saw wordpress’s login system was connected to all of the other stuff it installs but i want to be like, one server for logging in, so until they are in the same domain they are logged in…

The other sites run custom html files, made with dreamweaver…

http://www.wizard101saviour.godgivens.com/
http://kks21199.godgivens.com