For easy I like CSL halogen 120v under cabs. Each buld is 35w. The 1' has 1 bulb, 2' is 2 bulb, and 3' is a 3 bulber. Customer say they are bright. They have a built in dim setting on a switch but it's a poor quality and can see the light flicker. Never had to but you could use a normal dimmer. One limit to these is they only come in certain sizes.
For more extravicant I use the Juno trac 12: http://www.junolighting.com/productinfo/trac_t12_intro.asp
Juno does not seem to have all the parts listed on the web site.
I think Halo makes about the same.
You can custom fit them to any size. You can also adjust the spacing and bulb size for the customer. We use the smaller bulbs about every 3-4". Be carefull not to overload the end feeds. Of corse you would need a transformer (go magnetic) hidden in a remote place. You have to watch voltage drop. IF disired they should have special dimmers. Many LV dimmers have a low wattage rating (some 300) with out using other pieces ($$$). The wattage can add up fast with these. The bulbs seem to last years ard are easy to change. My money saving tip if using these buy your bulbs by the box from an auto parts store (#194 bulb).
Here is something simular but nerer used it: http://www.ccl-light.com/docs/undercab/cal.html
The same web site has rope & LED lighting. Here they made a point about UL delisting some rope light: http://www.ccl-light.com/docs/rope/2wirespecs.html
Rope is cheaper but I would not use it for the kitchen. It only puts out about 6w per foot. Not bright enough IMO. It can be difficult to try to get it to lay flat. If the rope twists while installing then it affects the lighting. Because the bulb is more on one side of the rope it will make bright & dim spots when twisted.