Has anyone implemented a login with wordpress?

[Prohibit]

Has anyone made it possible to use Wordpress as a CMS? Just a bridge between the client and the wordpress that keeps users synced? I probably sound like a huge noob asking this. I have a large community that I would love to go ahead and sync into my new retro so that I could just throw a 'enter hotel' button somewhere and it would popup and log them in. Even if that's not possible though, I am wondering if anyone has made a wordpress plugin that allows you to throw you php login form in the sidebar as a widget or if you could make a login page that would log you into the hotel.

Right now we have our wordpress & our xenforo synced up - which is also synced between our other xenforo installations. This would be the icing on the cake.