This site boasts that one can convert just about anything to anything else. And with 50,000 conversions and 5,000 units, it has an impressive range.
Sure, it has the popular conversions: length, temperature, speed,volume, weight, cooking, area, fuel economy, and currency. But it also contains measurements for women's clothing sizes between countries,light-years, density, torque, horse height, meeting room size needed for attendees, gauge and much more. There is even a Fun Stuff category that is practically addictive where users can find their age in dog years, convert their names into Morse code, determine their weight on Mars, and verify how many days until retirement! Indispensable.