Conversion of Miles into Kilometers, Dollars into Rupees, Pounds into Kilograms and any type of conversions can be done using the web service UnitConversion.org
To play with Mathematics go to MathPlayground.com
There are math games, logic games and puzzle games which increase the activeness, thought process and problem solving skills in players.
For English literature students, there’s Shakespeare-Online.com to know about Shakespeare, his works and related information.
ScienceMadeSimple.com is providing the wonders taken place in Science in the form of articles, projects & experiments. Here you can get all material on Science useful for elementary, middle school and high school students.
Video Lessons @Khan Academy
Khan Academy came forth with educational videos pertaining to students. Through YouTube we can see educational lectures and videos on math, science, chemistry, history, social studies and many more subjects.