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I can't take credit for inventing this idea, I got it from Dave Savery in the UK. I found his idea intriguing and decided to give it a try myself. It only took me $10 and a couple of hours to complete. I want to emphasize that, for me, this is an experiment. If it works out and the camera doesn't get waterlogged or melted from too much heat, I may expand on the idea around the house.
For my project I used a Logitech Webcam 9000 which had been glued to the inside of my trailer's back window for the last several months, showing what was outside. I had dissembled the camera when I first mounted it in order to get rid of the stand which wouldn't fit between the glass and the window shade, so that job was already done.
I purchased an inexpensive, outdoor, weatherproof, halogen light fixture at a home center near where we were camped the weekend of the project.
I then totally disassembled and stripped the fixture of all it's internal parts, discarding the light socket, wire, and internal socket support parts.
I had to cut the webcam's USB cable to be able to fish it through the fixture's support tube where the original wire went. I chose to cut the cable about 6 inches from the USB connector end so the repaired splice would be inside the trailer, rather than inside the fixture. After I had already cut the cable, I opened up the camera and learned I could have disconnected the wire from the camera circuit board and didn't have to cut the cable. Next time I will go that route. I would still have to use a soldering iron because the cable shield is soldered to the printed circuit board inside the camera, but the 4 USB power and communication wires use a small connector which would have fit through the housing easily.
To support the camera inside the fixture, I used some foam packing which came with a recent webcam. Using an Exacto knife, I cut the foam to fit the inside of the fixture. Then carved out a cavity to hold the camera. Another source for foam is available at fabric and hobby shops. Poly Foam which is used to make pillows, chair pads and such. I found a package which contains one sheet, 12 inches by 12 inches by 1 inch, for abour $2 at a Hobby Lobby store.
WARNING! Do Not try using expanding foam or bathtub caulk to mount your camera. After sealing the camera inside the fixture, the curing chemicals in those products will make short work of your camera, corroding and distroying the electronics within a very short time.
Originally I considered mounting the fixture to the trailer roof which would have been dificult to waterproof. Eventually I decided I could mount it to the back of the trailer and not have to deal with sealing all the joints as tightly. I am relying on the rubber gasket that came with the fixture to weatherproof the small cable hole through the trailer wall.
After reassembling the fixture with the camera nicely sealed inside, I mounted it on the back of my trailer, feeding the wire through a small hole in the wall. (see photo)
I didn't do a very good job of splicing the wires back together due to the fact I only have one working eye. The lack of depth preception gives me a great deal of difficulty getting the soldering iron, solder and wire to come together in the same place. But the splice is good enough to work for my needs.
The Live Camera 
Update March 31, 2013. This camera continues to perform well on the back of the trailer. The only prolem I have come across is I have to open up the fixture about every 6 months and clean the inside of the glass and the camera lens. It has a tendency to develope a film, probally caused by chmicals coming off the foam and depositing on the glass as the camera heats up and cools down. Other than that, the housing works well. I have even added another one called the Sunset Camera,whcih can be found in the list of webcams.