Below are some links to useful information about LED lighting technology.
Philips Online Lighting University (requires login)
Topics covered: LEDs and Trends, Myths about LEDs, Principle of LED, Principles of LED Systems, Applications for Indoor Functional and Architectural.
Topics covered: Lighting Terms, Lighting Technologies, Designing with Light, Standards and Policies
General questions about LEDs and lighting in a fun game form.
A pdf explaining lumen maintenance, published by Philips Lumiled division.
A pdf explaining LED testing, published by US Dept of Energy.