Since Tim is playing Calvinball and making things up as he goes, I must now submit my *own* web usability idea(s) using AJAX.  Man, don't you know I'm a bear of very little brain (and long words bother me)?  Think... think... think...

Well, if I were developing an e-commerce site -- let's take HandyShop, for example -- I would of course make it much more, you know, dynamic.  Like AJAX.  Yeah, that's the ticket.

The first idea that comes to mind is having a nice little shopping cart in some obvious location letting you know how many items you're currently bagging.  You find something that tickles your fancy, so you click on the "Add to cart/bag/buggy/wheelbarrow/pocket/whatever" and ... whoosh!  Instead of leaving the page, the number of items gets updated and the "Add to..." button changes in some obvious way to let the user know the exchange took place.  Maybe fireworks, a little fanfare, and some gratuitous bragging about how smart the shopper is.

My next grand idea: As you drill-down in the product categories through the menu or breadcrumbs... the user never has to leave the page.  Of course, I'm not sure this is 100% compatible with the browser's Back button.  Most users have grown accustomed to smacking the Back button willy-nilly.  I'm sure Jakob Nielsen has some kind of highly-scientific research to back this up.  But, what does he know?  His site hasn't changed since people were writing HTML with the abacus.  Come on, dude.  I mean, really.  It's a waste of CPU cycles for the Wayback Machine.  But, I digress...

Maybe if you had a very complex product that a customer could customize in some incomprehensible number of ways, AJAX could come to the rescue.  As the customer changed options, an AJAX request could make a trip to the server, build a new preview and present the user with yet more or different options.  Like building your own tricked out Pogo stick or extreme yo-yo.  That would rock.

There you have it.  I've exhausted my creativity.  However, keep your eye on Tim Haines blog, as I'm sure there will be lots of smarter people than me trying to crack this nut.