Washboards International: Dedicated to the musical washboard and its players.
Found on (where else) jugband.org, where you can dig this honkin jug virtuoso, or even build a washtub bass.

Though not strictly necessary, a tub-lifter can improve the resonance and increase the volume of a washtub bass. All that's needed is something to set the rim of the tub on to hold it a bit away from the floor. Most players use a small block of wood. Some cut a notch in the block to keep it from slipping. "Washtub Basso Rick" prefers to use the rubber head of a plunger, which yields the best results of all lifters I've tried.