SimplePie is a very fast and easy-to-use class, written in PHP, for reading RSS and Atom syndication feeds. By keeping it simple, and focusing on what?s important, we?ve built a pretty sweet little API. SimplePie?s focus has been two-fold: speed and ease of use, and has been very successful on both fronts.
I’ve tried quite a few on and offline aggregation systems, SimplePie allows you to aggregate and order entries in multiple blogs, as long as the feeds have dated items using the Multifeeds package. see SimplePie: Weblog » Sorting multiple feeds by time and date for details.
I like on of their taglines:
Feed parsing for the rest of us
So fast and easy you’d think we stole it from Apple
Given time I am quite interested in making something useful for one of these aggregators the way to go would probably be to build the html regularly with a cron job so that the browser would just load a fast static page.