Laundry detergent works well for me. Bleach to kill mildew.

Put 1 gallon bleach and 1 quart of Mean Green in a 5 gallon bucket then fill with water. Apply with a pump up garden sprayer. Running this brew thru a pressure washer will damage the pump.

TSP and bleach works well. I use Super Clean on the tough spots, absolutely the strongest cleaner you can buy short of some Zep products.

Jomax(found at Home Depot near the paint section) or Simple Green and clorex outdoor bleach. Mix about 1 pt of the jomax or simple green and 1 pt bleach to 3 quarts water. Should clean very well.

I'm not sure what type of pw you have, but be careful with bleach. Bleach will destroy you pw pump. If you have a downstream chemical injection system(most homeowner models do), make sure you clean your hose wand, and nozzles as bleach can ruin those items as well. I would spray the solution using a garden hose sprayer attachment, then rise with the pw.

Another option is to buy an x-jet for your pressure washer. I just found out about these kits. Its basically a special nozzle with a hose attached to it. You put the hose into you cleaning solution and install the nozzle onto you wand. That way you don't ruin your pw. I just bought a xjet for around 130 from Pressure Tek. I have to wait until it warms up around here, but this system has received good reviews on other sites.

http://www.pressuretek.com/m5xjet.html

Zep makes a product called Industrial Purple, sold at Home Depot. It has a pH of 14. A little goes a long way. I use it to clean my gutters/stains etc.