Gang,
I pre-soak shop rags, towels, & work clothes in the kitchen sink using HOT water and TSP. Then run them true the home washing machine (again with hot water and TSP). Then run thru the dryer as normal. They usually come out nice and clean. My dogs love to lay in the warm shop stuff while I'm folding them.
A note about my procedures... I don't use my shop rags & towels for really greasy or oil saturated work (like lubing the front spindles or wiping up big oil spills. I use paper towels with a degreaser to get all the old grease out, then do a final wipe with the shop towels. This makes the washing job easier and prevents contaminating the washing machine with horrifically greasy shop rags. It seems to work for me and my family.