I will recommend Ford. I've worked with all of them at one time or another, and have never been too impressed with the competition. I know people who have been very happy and well served by GM but my family has not had good luck with their vehicles and I will never buy one.
Dodge seems to be building a better truck now, the Dakota is a nice little pickup if your looking for something more stout than most compacts but not a full size, but again if you want a full size I say go with the Ford F series they're just a more solid truck thats better suited to work if you ask me.
You can get a new F250 with the 5.4 liter V8, 2 wheel drive, tow package, and the XL trim package which is vinyl with manual windows and locks for less than $25000 without too much trouble depending on the time of year and the number of dealers around. Thats what I'm driving right now, tow rating is 9,500 lbs and the gross weight rating is 8800 if I remember correctly. That puts the payload in the neighborhood of 4000lbs. I've only had about 6000 lbs behind it so far but you didn't even know it was there. The new triton engines are quiet and get pretty good mileage, and the truck handles like a cadillac, very nice ride. I prefer a manual transmission but the E4OD auto hauls well and is nice to drive. After you've had it awhile it programs itself to your driving and shifts nicely. The first few times out it will seem like its got a funny shift pattern.
If your looking for used, I still say go with Ford. The 302 and 351 (these will be in trucks with the old body style) engines are good work motors. Its not punchy,but you can put a load behind it and it will move it. Mileage isn't as good as the new motors though. They're easy to work on also, the guys that built those engines had worked on engines. You can change the oil without jacking it up or contorting yourself at all, and most of the other stuff is right there easy to get too.
If you can swing it, get one with a powerstroke deisel. At least if its from after 93-94 when they started putting a turbo on them, the ones without turbos are powerful and get decent mileage but they can be kind of doggy with a load behind them from what I've heard. The turbos are a dream though, tons of power and its incredibly smooth.
Figure out ballpark what kind of loads your going to be hauling weight wise and let that help you pick what size truck you want. In general, if you want a cheap work truck though the F250 is the way to go. You can get it stripped down and have more payload and power than an F150 with a lot of upgrades. The redesigned F150's are a little expensive to begin with. Look at F350's too if your going used, they'll be about the same in terms of price as F250's but have an even bigger payload. Gas mileage and handling are on par with F250's. Gives you a lot more options to look into.