The following resources cover more than one subject :D
[Khan Academy] Explanation Videos & Example Problems
Math • Physics • Chemistry • Biology • US History • World History • Health & Medicine • Grammar
Test Prep • College Admissions • Art • Computing • Economics
[Crash Course] Lecture Videos
Chemistry • US History • Ecology • Biology • World History • Anatomy & Physiology
Literature • Psychology • Economics • Government & Politics • Physics • Philosophy
Astronomy • Intellectual Property