Some utilities companies will drop off mulch for free if you ask them, but you'd probably need a dedicated dumping area set up beforehand. I use those free wood chips in 3 to 4" layers, with a couple of inches of compost between the layers. The compost traps and holds some water, keeping the mulch and the planted soil below it moist, and it feeds the plants as well. A mulch-compost-mulch layer like this will settle to somewhere in the neighborhood of 8" deep, yet remain loose and very easy to weed.
