We ran into the problem that the facility we use sometimes to dump our RV tanks here near home now locks their RV dump and only allows RVers to dump during business hours after providing a driver's license and $10 fee.
So we've turned to http://www.rvdumps.com
and it lists some locations of rv dumps that readers have sent in. We've added in corrections to some of the currently listed sites after using them and have added some locations we've come across that aren't listed.
If you are looking for a RV Dump site, try checking this out.... or adding in any you might know of.
EDIT 2/18/06: Just thought I'd bring this up again for the folks that don't know of this site.