SSH -- Running remote command and NOT Exiting

[Hal Vaughan <hal@thresholddigital.com>]

I know I can use SSH to run a remote command like this:

ssh newhost command-to-run

And if I have it set up to use RSA or some other type of authentication, it'll 
connect to the system, log in automatically, and run "command-to-run", then 
log out.

But I can't find anything in the man page (or on Google, but there's a high 
noise-to-signal ratio, including many copies of the man page) where I can 
tell ssh to run a command on login and NOT exit.  What can I do to make ssh 
login, run a command, then stay logged in, waiting for another command?

Thanks!

Hal