I usually feel very guilty about throwing out a zip lock bag when it's clearly still perfectly functional but just has some crumbs or something from whatever was in it last.**
I tried putting them in the dishwasher, stretching them around the prongs in the rack, but the force of the water usually sends them flying and they wind up at the bottom all rumpled up and soggy. I also tried washing them in the washing machine, but then you have the problem of how to get them dry.
I looked online to see how other people had dealt with the problem and noticed a couple of clever products: the washywonder and this one: the bag-e-wash and wondered how I could reproduce them.
**Note: mkambas made a good point which is you probably should not try to reuse bags that have had meat products in them before