Doing all things as unto the Lord.
Web forms will most likely be a vital part of your website, allowing you to gather information (including contact details) from your potential clients. Alot of people are making complicated web-based applications like content management systems. One of the advantages of Word was that it would automatically save your document every few minutes. Now your ajax-enhanced application can do the same.
We use AJAX in the "Start Building Your Website" feature near the top of every page on this site. If you haven't used it yet, try it out now. Type in your name and your e-mail address (don't worry, we don't spam and won't share your information with any third party). When you click Next, you're asked to create a password. Click Next again, and this page's content will change, but you're not really going to another page.
As you fill in the information, it is auto-saved every 60 seconds. That way, if your computer crashes or you accidentally go to another page or close the window, you can come back and start off right where you left off with little or no selections lost.
Our portfolio rotator also uses AJAX. You can see it at the top right of this site. It's drawing from our portfolio real-time. If we add another image while you're reading this, it will immediately be included in the rotation, all without your having to refresh the page.
One of the tragic dysfunctions of html is the lack of client-side includes. Ajax liberates. You can serve an order of magnitude more static pages than dynamic pages. But if you use ajax for personalization, the personalized components are also static. Suddenly, you scale better and don't need complicated component-level caching. Even better, the personalized elements have unique urls that can be cached by content delivery networks.