Colleagues Mark, Martin and Steve have pulled together a fantastic document that outlines some of the of mechanisms for extending Internet Explorer 8 and showcases work they’ve done with a number of UK customers (eg NHS search provider, Sky News web slice, Play.com accelerator - these are just a few examples).
The document includes a description of the features as well as an architecture overview, a gallery of UK customer examples, some guidance and sample code for enhanced web slices and, of course, links to plenty of additional resource to learn more.
There’s a great opportunity for businesses to build customized capabilities for IE8 for very little effort / cost. This document is a great place to get acquainted. You can download in either PDF or XPS format.