Originally posted by: Mark R
You may want to use the LEDs for lighting - signage, daytime visible indicators, backlighting of LCD TVs, etc.
Indicator LEDs like the ultra-bright blue ones that you can get everywhere these days are not powerful devices. They merely produce a very narrow, very intense beam - rather like a high-brightness flashlight. You couldn't use those for actual illumination.
You can get high power LEDs, but they are quite specialised. I'll include the obligatory pics of my collection of uber LEDs:
LEDs
Switched on
Switched off
My LuXbox