General
- The Book of Knowledge, which is seriously one of the best pages for learning things.
- Wolfram Alpha: It’s pretty cool (though some of their products are pretty expensive). A vast amount of data is available and the query structure is pretty robust. I often use this when I need mathematical or scientific data. Students may find it worthwhile to pay for the mobile application, which is a cheap way to get many of the pro features of Wolfram Alpha, such as step-by-step solutions for problems.
Science