I dump mine in FLYINRYAN'S backyard. No really I do, he has a sewer dump line.
Other than his place, I've stopped in Tecopa at the HotSprings "resort" and dumped there for $5. It's easy, gets it done before you get home, and plus it eliminates extra weight. Besides when you get home, you don't smell all them beer turds from sloshing around in the tank from the drive home.