New Users, and Conditional Tags

Hello. I have two quick questions to ask:

With WordPress μ, what is the tag, or link, to allow people to subscribe to make an account?

And, If a user is logged in, is there a way of writing some php to say ‘if user is logged in, display name, else display ‘visitor.’ ?

I’m no good at writing PHP!

Oh, and congrats WordPress on the new theme for your forums, and main site.

I like it very much.