If you go to http://webapps.stackexchange.com without having login credentials you get:
1) Redirected to a login page
2) The 'New here? check the FAQ' banner.
This shiny/obvious FAQ link results in the user returning to the login screen, without any FAQ goodness, and with nothing visible (that I could see) that there is a private beta running until you actually put in some OpenID details and try to login.
I'd suggest the FAQ for private beta sites include some details about having committed on area51 in order to access private, public beta start date, etc.