A List Apart: Articles: Test-Driven Progressive Enhancement
http://www.alistapart.com/articles/testdriven
"By testing a device’s capabilities up front, we can make informed decisions about the level of experience to deliver to that device. "
Automatic conversion from simple, accessible data tables to YUI Charts » Yahoo! User Interface Blog
http://yuiblog.com/blog/2008/01/17/tables-and-charts
"That’s all you need to do to progressively enhance an accessible data table to turn them into a pie chart using the YUI Charts Control."