A well known but not exactly accurate term, Hugelkultur, is a term that describes in Permaculture a type of garden bed that is built from burying wood products and sometimes compost under a layer of soil and mulch to provide a very healthy bed to grow your garden plants in.
Here is a good forum thread on Hugelkultur which explains it and has a lot of photos of people building Hugel beds on their land
There are lots of other sources as well if you do a search on Hugel, Hugel beds, Hugel kultur, Hugelculture, Hugel Beets, etc...
I have begun to build Hugel beds on my property and have been seeing some very good results. We heat with firewood with our outdoor wood boiler for our house and our son's next door. We started out our first hugel bed areas by burying bark that fell off of our firewood deliveries in shallow trenches on the property, adding some compost on top and then putting the soil from the trenches back over the top of the beds and planting them. These beds were very productive and held water very well needing very very little irrigation. (we use drip irrigation and did use it occasionally during the drought)
Another area we buried lots of branches and old lumber scraps under an ongoing compost pile, and then spread the compost pile out over a large bed the following spring. The wood parts in the pile were beginning to decompose but had not yet decomposed completely, so we spread this out over an area about a foot thick and then put a layer of clay and soil over and planted it.
Both of the above areas grew disease free healthy potatoes, although they were a bit difficult to dig with the clay and some decomposing wood pieces..the cole crops grew very well on them, the corn didn't grow quite as well, but the tomato and beans and other crops did quite well including greens.
A couple of the beds that we built, we planted some dwarf apple trees into, and those trees did very well also, we surrounded them with multplying onions, chives and some annual vegetables.
In our small forested area where we are putting in trails, we have been burying branches and dying trees and some tree trunks under clay/sand/soil removed from the pond dig. These areas are very fertile and in the next few years will be planted with food and ornamental plants into the forested area along the trails..cuttings, seeds and plants as we have them available.
In most cases hugel beds are made by piling larger logs and or wood pieces of any sort (but not treated) on the ground or in a trench. The wood pieces can be covered with smaller branches, leaves, compost or whatever materials you have on hand and then covered with a layer of soil. It is best to cover the entire thing with a thick layer of mulch if you have the materials available..and water it well as it will settle out the air pockets.
If you have any manures it is good to add them to the woody layer, as they will counteract the nitrogen loss from the wood decomposing, and it is also a good idea to plant nitrogen fixers in your hugel beds during the first year..such as beans, peas, legumes, clovers, or even larger nitrogen fixers such as pea shrubs, eleaganeus, and others.
Another wonderful product to add to your hugel beds is char. You can make your own char (search on line or go to http://www.permies.com/ and search char) or you can save the unburned char from your fireplace or wood stove and add that to the soil of the hugel bed or anywhere in your garden. Wood ash is also a good source of nutrients but avoid using it where there will be a need for acidity in the soil such as for blueberries.
We also have an area of our property where we had alder trees and cattail roots that were buried under clay and sand in a pond dig area..and those were left to decompose beneath the clay and sand and that area is being planted with a wide lawn path/road over the center and along the sides is being planted with trees and shrubs and perennials on both sides..since the piles were levelled out along the North bank of the pond and into the woods to the North of that..Many of the plants for this lawn/road/bank/bed area have already been planted and are growing quite well...although the drought has been effecting a few things with the clay baking in the sun. Grass was just sown to the road/path/lawn area this month and is starting to grow, but a lot of it ran off in a heavy rain and will have to be replanted.
There are also some lower areas on the property that we are using wood chips, branches, plant refuse, tree parts, clay and sand to fill in and level out low areas. Those won't be finished for another year or so and then they will be planted as we choose at that time.
We used to burn our excess woody refuse but now we are burying it into hugel beds, a much better use of the woody refuse and better for the environment.