I used the cheap power supplies that pop up with the lights on Amazon. I don't know if they're dim-able, but they work. The local electrical supply sells a very good quality and very small transformer for $40, I'll get those if the cheap ones fail.
To power the under cabinet lights I had to get power from the range hood. I added an outlet above the hood in the cabinet and plugged the transformer in there. I used a $20 remote control outlet to switch the lights. I could have used any small switch on the 12 volt side, but I didn't want the transformer to run 24/7.
I stuck the lights directly to the bottom of my cabinets, in some other areas I picked up aluminum channel with a plastic lens, and mounted the lights in that.
You can see the lights reflected off the granite counter tops, and you can tell it's individual lights.
I had some corners to go around, and needed to power from the center of one strip, so I just soldered jumper wires on the strips anywhere I needed them. You can use almost any 12 volt power source, like an old computer power supply, and you can also use them in your car and power them right from the battery.