Can you run 2 X/KDE sessions at once?

["shrevie@ntnation.com" <shrevie@ntnation.com>]

Is it possible to run two different X sessions at the same time as two
different users?

In other words, I want to hit ctrl-alt-F3 (for example), login as
another user, and run X and KDE while having my regular X/Kde session
running on ctrl-alt-F7.

When I try to do that now, I end up with an X error because it can't
open Display 0:0 (since that's already in use of course).

Thanks for any help or ideas!

Moe