If you really are interested in the luxeon LEDs then here is a basic run down of what you need to know:
Ignore the 'emitters', 'snap leds' etc. - all you are interested in is 'luxeon star'.
There are 2 main types:
1) Narrow beam (called star/O) - these are like a normal high-brigtness LED with a very narrow, very bright beam.
2) Everything else - Don't worry too much about lambertian and batwing - they're very similar, in that they are 'flood lights' pumping out light in every direction (like a normal light bulb). The lamberian patten is slightly smoother - the batwing has a dark spot directly in centre of the beam.
They also come in several power levels:
1) Luxeon
2) Luxeon III (3x the power, 1.5x the price)
3) Luxeon V (4x the power - but too expensive, so ignore these).
I would recommend using a standard luxeon star. You should get good results if you connect a single blue star to the 5V supply using a 3.9 Ohm 1 Watt resistor.
If you want to use the more powerful luxeon III. Then I would recommend using a 1.8 Ohm 2 Watt resistor and connecting to the 5V supply. You must use a heatsink with Luxeon IIIs - an old 486 heatsink should be fine.
I normally buy mine from
Luxeonstar.com