Have added a download possibility of the CP/M Walnut Creek CD here.

Many (not all) files can be found also here.
The original Simtel website doesn't offer these files anymore, see here.

A few rare files can be found also here.

It's a pitty that there are not many other possibilities.

Because of popular demand - here are some other links, and with a full BEEHIVE branch:

gopher.floodgap.com
www.scovetta.com
z80cpu.eu/mirrors/
ftp.catcorner.org
maben.homeip.net (BEEHIVE missing)
ferretronix.com/march/ (BZIP2 compressed archive)

Added later: There's another ISO image at n8vem-sbc.pbworks.com available.