iGoogle is Google's answer to the seemingly ubiquitous portal page competitors like MSN and Yahoo toss at their users. A single page for the user to collect all their most used and referenced information, links and content. I personally use mine for RSS feeds, weather information, daily comics and more. It's a great tool.
Plus, it's almost completely customizable. Content on the page is broken up into blocks, which you can rearrange, reassign etc. Recently, Google added the ability to load one of several themes, changing the general feel of iGoogle, letting you get away from the blue/white of the standard Google design. At first there were only a handful of themes to pick from, but over time they've expanded. Today though they've taken another step in customization. Now users can create their own themes and share them with others.
Using the iGoogle Tools and Themes API, people with an eye towards web design can make their own themes and share them with friends.
So if you're an iGoogle user, or someone with a knack for web design, take a crack at it and let us know how it works out.