The short answer is that many types of aquarium water pumps will work, and how you attach the pump to the water changer depends on the pump. I now do it in a variety of ways. Below are pictures with some explanation.
For starters, you need to consider how big a pump you are willing to use. A bigger pump will move water more quickly, but it can be harder to get the pump in and out of the tank. A small pump that works well is the old Marineland Maxi-Jet, no longer sold by Marineland. Cobalt's MJ pump is very similar (I think it's made by the same folks). For this pump, you may be able to remove the gravel vac end of your water changer, then slip the hose over the output on the pump. For my water changer, I had to put a smaller piece of tubing over the output on the pump, then put the water changer tubing over that:
This works well for smaller tanks, but doesn't move the water all that quickly.
For another pump, I was able to put a length of larger tubing over the output tube, and attach a hose fitting to the end of that tube. You can then attach the faucet attachment of the water changer to the hose fitting, as shown below.
This gives you a little more flexibility in moving the pump from tank to tank.
Finally, I've got a bigger pump that has a threaded output, and I can attach the faucet attachment end of the water changer to that.
This moves a lot of water quickly, but is a little awkward.
If you really want to move a lot of water quickly, you can consider the fancy options at JEHMCO:
http://www.jehmco.com/html/safety_siphon_aquarium_drain.html
JEHMCO also sells lots of pumps, as does Kensfish. You can also pick up a pump at your LFS, if you have one. Finally, people sell pumps on eBay, of course, and you can find bargains there, if you have patience.