[OT] Anyone experienced with white LEDs?

I'm looking at building a personal lighting project possibly using white LEDs instead of regular miniature bulbs, and as I browsed the Mouser catalog, I got a whole lot more confused than less... I'm trying to get the maximum amount of light for current expended, and the numbers seem to be nonstandard, or at least not enough info is provided... :-/ Example: P. 217, "Super Flux LED Lamps" The white one shows at 20mA it will put out 400-600 "Iv (mcd)" P. 216, "Blue & White LED Lamps" The brightest white they have is listed as: "2200->3200 "Luminous Intensity" but with no mention of current or value (mcd? ucd? ) P. 199, "Thru-Hole White LED Lamps" "Luminous Intensity" ? current would output 1.7->2.3->2.6 (min/typical/max) mcd... and on P. 206, there's a few colored LEDs output listed as "Foot Lamberts"... And Digi-Key has these Surface Mount Incandescent Lamps... :-O The look cool, but how hot do they get? (It's a very small installation area... It's still an idea I'm forming, but if it works out, it's a *kewl* idea...) Any good websites w/info on how to figure out how many LEDs I'd need to make about a 40W (or more) lightbulb worth of light?