Not after every use. I probably wash them after 3 though. It depends on what they were used for. I have seperate towels for buffing off waxes and sealants and polishes. Its nice to keep them seperate. They all get washed once a week pretty much regardless of how dirty they are. If nothing else I have to wash at least my waffle weave because it starts to smell after drying 8 or 9 cars. I need two of those.
Do you have a garage or are you organizing in your trunk? There are several threads with people posting their organization pictures. If you did a search on the word "organize" or other related words then I'm sure you would get some good threads with pictures.