Drizzle
Drizzle is a powerful Uru tools with many features covering very different aspects of the game. Most notably, it features the Uru Age Manager and a tool to convert ages from various Cyan games to Uru. Up-to-date Drizzle information is available on the Drizzle wiki.
Installation
Drizzle requires Java to run, so you first need to get that from the Java website unless you already have it installed.
Now you can head to http://sourceforge.net/projects/drizzle/ to download the latest version of Drizzle. "Drizzle??.jar" is the actual program, it should usually be launched on double-click. If instead some archive application starts and shows the content of that file, the default launcher is configured incorrectly. Right-click on the Drizzle file, choose "Open with", and then select Java to properly run the application.