Fetching remote password protected pages

[Tom Cook]

I'm trying to put together a script that will allow a user to:

a) log in to the script
b) once logged in, be presented with links to other sites that all
require regular HTTP authentication.
c) have the user click on the links and automagically go to the other
sites and be logged in there BUT I don't want the url or status bar to
look like "http://user:[email protected]" because that's pretty
insecure.

I've already got the part about logging in set up and working, but how
can I construct the site so that the user is either (a) already logged
when they click on the link (like logging the user in before they even
see the link) or (b) having the credentials sent to the server in some
other way through the link.

Thanks for any answer!