I have done some work recently using RSS as a means to feed content to a portal. The RSS feeds themselves can come from external sites or be distributed over the multiple servers. A caching RSS server can then be used to limit the impact on the backend systems.

For example - a personalised page can contain office news, local weather, my e-mail inbox, News from my favourite feeds etc. These can all be supplied through a caching RSS server with the cache refresh set to different rates. My inbox refreshes every five minutes whereas the news is once every half hour.