Just found this great site! Many of you may already be using this idea but just in case:

I use 50 gallon plastic drums cut in half. Holes are drilled around the bottom for drainage and the half-barrel is filled halfway up with packing peanuts (to keep it from being so heavy). The top half of the half-barrel is filled with planting meduim. This creates a planter that is approximately waist high when you are in the sitting position and is accessible from all sides. I also have 3 two hundred gallon planters that were used to transport palms to be planted at a local airport. I use them to plant my tomatoes, peppers, and so forth. In the winter they hold cabbage and lettuce and sometimes I just use them as a holding container for things that I don't know what to do with yet. The big planters are about waist high when I am in the standing position.