My first experiment with OpenCalais involved OpenOffice. I use OpenOffice intensively (as a direct replacement for the Microsoft Office line of shovelware), and although OpenOffice (like Office) has more than its fair share of annoyances, it also has some features that are just plain crazy-useful, such as support for Macros written in any of four languages (Python, Basic, beanshell, and JavaScript). The JavaScript binding is particularly useful, since it's implemented in Java and allows you to tap the power of the JRE. But I'm getting ahead of myself.