Khan Academy (Free videos that cover mathematics and physics from kindergarten level to college freshman level)

The Theoretical Minimum (String theorist Leonard Susskinds homepage where you can find free video lectures)

Physics Stack Exchange, Physics forum (You can ask any physics questions here.)

The Official String Theory Web Site (website with useful resources for laymen)

The Elegant Universe (a TV program based on string theorist Brian Greenes book, The Elegant Universe)

Project Tuva (Feynman video lectures online by the courtesy of Bill Gates)

String Theorist Shiraz Minwallas homepage (string theory video lectures online)

Modern Physics: Special Relativity (8 video lectures online)

Einsteins General Theory of Relativity (12 video lectures online)

Modern Physics: Quantum Mechanics (10 video lectures online)

A theoretical physics FAQ  (containing 140 common questions)

String Theorist Edward Wittens homepage (webpage with articles for both laymen and physicists)

Abhay Ashtekar: Semi-Popular Articles (articles aimed at the general public, written by Abhay Ashtekar, one of the founders of loop quantum gravity)

Atoms of Space and Time (an article by Lee Smolin, one of the founders of loop quantum gravity)

How to become a GOOD theoretical physicist (some pieces of advice by Nobel Laureate Gerard t Hooft)

MIT OpenCourseWare (Free Online MIT Course Materials)

Google groups: sci.physics.strings, sci.physics.research (google groups where you can ask questions)