Since BOOmbOOm brought up this style of camper I figured I share a few manufacturers
Four Wheel Truck Campers They make some very nice campers that can be mounted onto flat bed truck or slide in for a standard truck bed.
Palomino Truck Campers They offer both soft side and hard side campers.
Alaskan Truck Campers This from what I remember is one of the original collapsible type campers and have been around for years. I can remember this brand from back in the 60's even.
As has been pointed out there are so many options out there for the different styles and options of campers that of course what works for one may not work for the next person. There are also some CUSTOM built truck campers available out there. What you choose to spend is sort of like deciding on how much to spend on our Jeeps. The sky is the limit and you can have just a basic place to sleep out of the weather or go all out and have a camper that is close to the size of a small apartment if you choose. Fresh water & gray and black water holding tank sizes varies from brand to brand and by size.
As Turbo TJ said you'll be surprised at how much things actually weigh once you're loaded and ready to roll. It helps to run your rig across the scales just to see where you at once you have everything loaded up. I hope this helps others out for those who are thinking about purchasing a truck camper at some point.