We've been beekeeping with traditional (Langstroth) hives for a few years now and have been interested in the top bar approach for some time.
The idea is that the hive is a single V shaped horizontal box. "Bars" are hung on the top of the box and a cover is then placed. These bars have no foundation. The bees build their combs straight down from these bars. Because there is no foundation, you don't use an extractor to get the honey. You simply cut the comb from the bar and then there are many ways to process that comb of honey.
These boxes can be as simple or complex as you'd like, and anybody could build one. The big downside that I can see is that you can't add supers to expand the hive. In other words, once the hive is full, there is no chance of expanding it.
I can easily see having 5, 10, or even 20 of these topbar hives spread around the property.
There is a document that describes a very simple and easily built top bar hive at
the barefoot beekeeper's website.
Also, TJ Carr, a beekeeper in Albuquerque, has posted amazingly detailed and professional plans for what looks like the ultimate top-bar hive, complete with a window so you can watch the bees at work! Links to download his plans are:
Description of the plans [PDF]
The plans [PDF]
TJ's hive looks beautiful and I'm planning on making one (or more) for ourselves this winter, so I can have it ready for the inevitable springtime swarms!