The Lunatec Trekr self-cleaning washcloth is a simple thing, but it just works. At some point in my life I pretty much gave up on the washcloth because they didn't dry and quickly got nasty. This new washcloth has brought me back into the fold. It is a simple nylon mesh washcloth with an elastic loop at one end (for hanging or holding it packed up) but its open weave allows it to drain and dry almost instantly. It hold suds well and is abrasive enough to scrub off grime without painful scouring. I've had one hanging in my shower by a nite-ize gear tie hook for a year now and it is always ready for another scrub. About the only downside I've found is that it doesn't hold a lot of water for sink "sponge baths" when traveling which is more than offset by the easy cleaning and quick drying.
Full disclosure - I was given a washcloth for free at the OR show.
It is available in blue and gray and two sizes, 11"x11" (10g) and 12"x36" (24g).
Lunatec page on the Trekr Self-Cleaning Washcloth