The question of dimmable led lights is not well documented because the technology is new and changing quickly.

The Low voltage small bulb LED fixtures like under cabinet lights ,and some track lighting are only dimmable with an in line LED dimmer after the LED driver, or the driver itself is a magnetic dimming driver that is dimmed with a house magnetic low voltage dimmer. Only the external driver type fixtures work in this situation, and not the direct wire. Please do your own research on this matter because technology changes quickly.

The 120v direct wire small bulb LED under cabinet, pendant, and track lights are not dimmable, as far as I know. Update- Kichler has a new model of a direct wire dimmable LED under cabinet light, dimmable with a regular house dimmer. See this light here: Dimmable LED Under Cabinet Light.

The Nora Lighting NULB series 24v is an under cabinet light that offers an in-line LED dimmer, as well as a magnetic dimmer capable driver. If you must have dimmable LED under cabinet lights this is the way to go. The only draw back to the low voltage stuff is all the extra equipment in transformers, dimmers and connection cables.

There are recently LED large bulbs that are made to work with a regular 120v dimmer switch. These Led replacement bulbs come in regular screw  incandescence type bases as well as other fluorescent type bases. Go to this web site for more information on dimmable Led lights http://www.earthled.com/lumiselect-dimmable-led-light-bulbs.html