http://www.pdpplanet.com/
They have a Tops-10 and a Tops-20 you can get an account on and login to.
There are emulators out there too. And SCO released PDP-11 version 5,6,7 unix for non commercial use w/ source awhile ago. With source!
I'm sure there are Vaxen logins available out there too.
--
The Penguins are psychotic - Marty
