Last fall, because our yard is "challenged", we put in a "hugel" bed. Basically, what this is, is you begin with branches and brush, make a mound with what you have. Add to that any leaves or yard waste, we were able to source some free chicken manure and some straw and we let this area sit all winter to compost down.
In the spring, we sources some free wood, not pressure treated, but heat treated, that was being thrown away and DH gave the hugel three sides with only the purchase of screws.
Then, the bucket brigade of free compost began until the hugel was "full". Really, I ran out of steam from getting over 50 five gallon buckets full, just for the hugel. Also added in were a few bags of mushroom compost, peat moss, and free bags of coffee grounds.