What is the brightest, biggest & baddest white LED to date?
Luminius devices SST-90 is a 9mm^2 beast of an LED that can chuck out a massive 2000+ lumens. - http://www.luminus.com/products/SST-90.html
The CREE XM-L is also a nice device if you want something smaller.

Note that for a projector you want to produce the light in the smallest possible area and as such - those big "panel" like LED's are no good to you. 

There is an epic thread that you no doubt would have come across while searching about DIY'ing a LED projector - http://lumenlab.com/forums/index.php?showtopic=24619
Has heaps of good info in there ;)