I've been posting a lot on raised beds, but we haven't actually talked about building the raised bed itself. It can be as easy as a few boards nailed together, but if you want it to last more than a couple of years, it takes a little more planning.
If you live in an area where termites are a problem, you can do it with metal. Eat that, bugs.
You can even raise your raised bed, so if you have problems bending over, you don't have to. I couldn't find a video for this, but from my reading (haven't tried it myself) it usually involves the use of cinder blocks, railroad ties or something similar to build a base for the raised bed. The raised bed doesn't weigh as much as you might think because the soil mix is much lighter than normal earth. The big trick is the floor for the bed, which must hold in the soil but provide for drainage. I'm thinking something like hardware cloth with a fine screen laid on top.
Yeah, you can get pretty carried away with this stuff.