I've used:
1W LEDs - Luxeon star, 3 warm white and one cool white (it probably should have been the other way around since the plants need more of the "blue" light of around 450nm tech. sheet you can get alle info you need here


3W LEDs - Seoul zled p4, 2 natural white. I found that this color should provide a good basis for phot synthesis with peaks in both 450 nm and aprox 600-650nm Tech. sheet

I just read something today regarding white LEDs, that they are actually phosphorised blue leds that emmit light that for us looks like white light but really isn't and that the plants are not "fooled".. I have no idea whether this is true or not - but if it is, I just wasted alot of money on my setup! I'm hoping it's not, and since the manufacturers can provide spectrums of the light showing peaks as I mentioned before I think I'm good with my setup, but who knows?! In any case blue red or amber colored LEDs could be used to create a perfect spectrum for the plants, however it might not be that pretty in the living room or windowsill...

I'll snap some pics of my setup a little later today.

Christian

Edit: Another really good bet would probably be Luxeon K2 Tech. sheet
 I didn't use these since they need a constat current supply of at least 1000mA, and the LED drivers readily availible only go up to 750mA, and this can easily drive the Seoul p4's (they can also handle 1000mA though). If you have some tech wiz on your side you should really look into these - I believe I read somewhere that they can hadle temperatures of up to 125 degrees celcius with out taking damage - which lessens the need for additional heatsinks..
Oh and another thing is - they come in more colors that the seoul p4, but you can see this from the tech sheets

In any case, if you choose to go for highpower LEDs you should also look into collimator lenses, since the LEDs emmit at an angle of around 100-130 degrees, and the FC or lux would be way to low. Something like 5-25 degrees would be prefferable depending on how far above the plants the lights are fixed. I believe that there are companies called Carclo and Kathod that produce them..