Optimum No Rinse Wash & Shine if the car is just "regular" dirty. Works great and no scratches. Must use top quality microfiber towels though. I can wash my whole car, using the two bucket method, with only about 8 gallons of water. This is nice since we are still officially in water restrictions around here. You can also pull it into the garage and give it a good was in the cold winter.
If it's really nasty, I use the Optimum Car Wash. It's very nice stuff.
In fact, I use all the Optimum Polymer Technologies products. Very good stuff!