I am occasionally noticing outbound mail getting stuck in 
/var/spool/clientmqueue.

According to
http://www.sendmail.org/secure-install.html
the solution is to start a "client queue runner" with the command
/PATH/TO/sendmail -L sm-msp-queue -Ac -q30m

I don't see anything in /etc/rc.d/sendmail that would start this queue 
runner for me.  Should something be added to do this, or am I missing 
something?  Should I add the command to /etc/rc.local (seems 
counterproductive as I'm surely not the only person who needs this...)

Cheers,
entropy