Caching at the Edge of the Network
In WCM there is always a tension between caching content closer to visitors for performance reasons versus doing useful real-time processing like dynamic navigation or personalization. Content Delivery Networks (CDNs) like Akamai -- the folks who brought us ubiquitous image and video serving from around the 'Net -- are now experimenting with network caching of dynamic content too. Together with Oracle, Akamai has developed a mark-up language called "Edge Side Includes (ESI)" to provide a standard for the caching servers to take on just enough of the processing load. It should come in handy for Web Services as well. Some CM vendors like OpenMarket (now divine) have experimented previously with these types of approaches, but are now signed on to the ESI initiative...
Visit ESI.org for more info