Jerome Fine replies:
There is also a commercial version of Ersatz-11 for Linux.
With the recent release of Ersatz-11 V3.1, there is now a demo
version for Linux as well. And the limits on the demo versions
have been relaxed a bit. It's quite usable for hobby purposes.
http://www.dbit.com/demo.html
SIMH is very good, but E11 is a truly industrial-strength PDP-11
simulator. Of course, SIMH also simulates a lot of systems other
than just PDP-11s, from DEC and from other manufacturers.