After searching in vain for an unobtrusive, lightweight javascript calendar, I decided to write my own. It's flexible enough to do what I need, and doesn't take much effort to get it working.

Diablo 3 Stat + Build Calculator for DPS and Toughness
A Google spreadsheet to import your Diablo 3 character builds and make accurate comparisons.

A simple cross-browser XMLHttpRequest (AJAX) wrapper.