Simple memcached question

1) What is the best resource/tutorial for learning how to set up
memcached with Rails?

http://dev.robotcoop.com/Libraries/memcache-client/index.html

There's also some plugins that will let you use memcache for sessions/cache/models, etc...

2) Is the memcached server accessible to many client _machines_ so that
my cache can be available to all of the servers in a Mongrel cluster?

Yes.