We recently did a talk at GTAC (Google Test Automation Conference) on "building a flexible and reusable test automation framework around Selenium-RC". Here's the link to the talk and to our slides. Please let us know what you think :)
video: (see below) http://www.youtube.com/watch?v=hWQdCdH77NA
slides: http://apple.chow.googlepages.com/GTAC_SeleniumFramework.pdf
One lesson we've learned is that some people are allergic to XMLs :-) Though it has been working quite well for us, we are planning to refactor our code such that people can describe their UI pages using java objects, XMLs, property files or whichever way they choose as long as they conform to our interfaces.
If you have other comments regarding our approach/design, please let us know.