This is a video of a game which replicates Portal's physics system in 2 dimensions on the TI-83 graphic calculator. The game was developed by a 20 year old student studying game design. A download link is available here.
Scientific calculator. Graphing calculator. Fraction calculator. Unit conversion calculators. Inflation calculator. Fuel cost calculator. WPM calculator. Homework assignment timeline calculator. Stock valuation calculator. Distance calculator. Meteor impact calculator. Currency calculator. BMI calculator. BPM calculator. [more inside]
If this doesn't convert you... you may truly be lost.
Webcalc solves over 100 different equations online.
Find the distance between two American telephone exchanges with the Interoffice Mileage Calculator. Find the distance between any two cities in the world with How Far Is It?. The latter also has a full database of American and Canadian towns, so I know that my hometown is 4864 miles from Athens, Greece, and 768 miles from Athens, Georgia.