This is part of a ongoing project to replace as many of the common bulbs and halogens as possible with LED's. This time it's a book shelf light from Ikea thats being modified.
The halogen was taken out and a Luxeon Star K2 took it's place. The reflector doubles as a cooler, a piece of copper foil is placed underneath the Star to help conduct heat.
A driver based on Maxim's MAX16820: