Google Blog notes:
The personalized homepage was created to bring together the stuff that interests you from across the web. With the Google Homepage API, developers can now create modules for the personalized homepage. It's designed to be flexible and easy to use, and you don't need to download anything to create a module. To get the ball rolling, the team's created a few modules to add to the directory. So check these out and get started creating your own.
Google Homepage API lets you add XML modules that wrap existing content or applications.
Here is an example of a module that just uses HTML. This module displays a clickable photograph that opens a photo album in a new HTML page:
<?xml version="1.0" encoding="UTF-8" ?>
<ModulePrefs title="Go to Photo Album" height="250" scaling="false" />
<a id="Riggs" title="My Photo Album" target="_blank"
<img border="0" alt="Photo"