Flickr is almost certainly the best online photo management and sharing application in the world. Show off your favorite photos and videos to the world, securely and privately show content to your friends and family, or blog the photos and videos you take with a cameraphone.
CK-12 Foundation provides a library of free online textbooks, videos, exercises, flashcards, and real world applications for over 5000 concepts from arithmetic to history
Dictionary of Numbers is an award-winning Google Chrome extension that tries to make sense of numbers you encounter on the web by giving you a description of that number in human terms. Like a dictionary describes words you don't know in terms you do, Dictionary of Numbers puts quantities you're unfamiliar with in terms you can understand.
Learn for free about math, art, computer programming, economics, physics, chemistry, biology, medicine, finance, history, and more. Khan Academy is a nonprofit with the mission of providing a free, world-class education for anyone, anywhere.
IXL is the Web's most comprehensive K-12 practice site. Widely used by schools and families, IXL provides unlimited practice in more than 3,000 math and English topics. An adaptive learning system features games and awards, inspiring students to achieve.