Not sure that it has all of the features you want, but I really like restful-authentication.
http://agilewebdevelopment.com/plugins/restful_authentication
Features per website:
Login / logout
Secure password handling
Account activation by validating email
Account approval / disabling by admin
Rudimentary hooks for authorization and access control.
It also makes an appearance in a screen cast over at http://www.buildingwebapps.com/learningrails
Episode 11 about adding User Authentication. Watch the others if you are 100% new to rails, but if you just want to see them use the gem, skip to that one.