I want to use XML for my Blog, so I've been reading up on the issue for a few days now. Here are some things you might be interested in.WebReview.com: RSS Delivers the XML Promise » "RSS (Rich Site Summary) is an application of XML (eXtensible Markup Language). In essence, RSS is a file format that uses XML. It can be created easily by hand or by any web content management system. The RSS core file defines a 'channel'. Surrounding this core file are a number of tools, services, and protocols that, while not strictly RSS, extend the power of this simple format to the point where it can compete with many high-priced commercial content-sharing and syndication systems."
I think I'll use BlogFeed for my blog. This contains a number of PHP files which convert your blog to RSS. And as a bonus, also communicates the updates to Weblogs.com. Oh, and here's a link to the Google directory on RSS.