JConvert 1.0.2 Beta
Jconvert enables you to convert between dozens of measurement units, covering the most varied fields: from length to temperature, from time to computer units.
The program looks really simple and works in a very simple way as well. Simply run the JAR file (no installation required) and you'll be presented with a fairly basic interface divided into tabs.
Conversions are done in real time as you type your values. Although there's a wide range of measure units covered, you can add your own, but only by editing a text file.