Most local power companies have a program that provides free wood chips. Here is one example from FPL in South Florida:
"When our line-clearing contractors are trimming trees in your area, you may be eligible for free mulch. Once FPL’s line-clearing professionals have completed work in your area, they will use a wood chipper to grind the tree limbs and branches into mulch. This type of mulch is different from store-bought mulch, which is treated and made from one kind of tree. The quality and consistency of this mulch varies considerably, depending on the types of trees and leaves removed during the tree work. FPL does not recommend this mulch for aesthetic use in formal landscape beds, but rather for use around trees and other plants to:
Maintain soil temperature
Reduce weeds and grasses
Provide nutrients to the soil, and
Reduce wind erosion from uncovered soils.
Orders for mulch are filled based on a minimum of one truckload. This is equal to 14 cubic yards of mulch, which is approximately 130 bags from a retail store or 25 wheelbarrow loads. To order free mulch, call the phone number on the letter or door card you received to request an application."
Here is an example from Arizona: How I get Wood Chips for FREE in My Garden:
Where to Find Safe Mulch - The Survival Gardener http://buff.ly/1WBpdyp
Citizen Forestry Manual. Miami-Dade County (PDF).