Using XML to Assist Search Engines
This tutorial explores a feature of Google's search engine called Google Sitemaps, which allows Web developers to automatically notify Google of changes in web page content so that Google can know that the pages exist, as well as indexing the pages more frequently. Of course, Google Sitemaps uses XML or I wouldn't be bothering to tell you about it. It represents a clever and efficient use of XML that serves as an important tool in any Web developer's toolkit.

Using XML to Hack Google Maps
Google Maps is an online mapping tool that is without a doubt one of the coolest online resources I've ever used. Online map services aren't really new but Google Maps is so unique in its map interface that it is truly a groundbreaking application. In this tutorial, you'll learn: How to create a complete XML-based custom Google Maps application.

Submit your sitemap.xml to google
Submit your wordpress.com sitemap.xml to google and verify it

XML (New Techniques)
How to use XML to mine data on the web, how to use it to interact with existing data services such as iTunes and Google, and how to use it in applications such as e-books, online speech synthesis, and multimedia.