I just stumbled upon http://www.webtogs.co.uk/ an AJAX enabled e-commerce site with a wonderful balance between AJAX, usability and design.

One of the well balanced functions is when the user need to select color and size - sold out "combinations" is showed instantly as well as the estimated delivery.

Notice - the cursor delay when moving over the buttons is due to the screen capture software - when browsing the site without screen capture there is no delay.

Watch the video or check it out yourself on http://www.webtogs.co.uk/.

I was thinking if it could be of any interest to post this at all, but now I’m doing it anyway.
When I was surfing for great AJAX usability experience, I ran into buyersvine.com where the search usability has ended up in a total disaster.

Buyersvine.com has created a drag and drop search function, I’m not sure if it’s right to call it AJAX, it’s more a DHTML implementation; but no matter what technology it is: it’s a classic example of a “because-it-is-technically-possible" misunderstanding.
On the search page they ask people to drag and drop search terms (called "search tags") from several lists to a collection of search fields. It not easy to do, especially not if one need to scroll the page at the same time.
One have a lot of search options to choose from, covering everything from the reasonable "Wine by Type" and "Wine by Price" to the more uncommon "Wine by Day" (what about a wine special usable for Wednesdays??), "Wine by Sport" not to mention the "Wine by Profession" (I never realised before that some wines are especially suitable for professors and others for poets).

What isn’t obvious is that the search is combined with 'and' between the search fields: if one selects the price range 50-70 and 70-90, the search shows up empty – because no wine cost both 50 AND 70 USD. At the same time: there are no results for at lot of the suggested "search tags" e.g. on the day tested the site didn’t have any wine in several of the suggested price ranges.

This search could have a huge usability improvement if they:
• Remove the drag and drop functionality
• Indicated next to the search tags how many results one can expect (e.g. "$150-170 (0)")
• Make users select the tags by checkboxes (when multiple can be selected) and radiobuttons where only one selection makes sense (for "Wine by Price", "Wine by Region" etc.)

A great example that less is more

See the video or try it out yourself on http://buyersvine.com/Tags

Cofman.com has this great search filter for finding available summer houses.

Instead of making people fill out a lot of search criteria, click the ‘GO!’ button and then have the result: we don’t have anything meeting your search criteria. Cofman give the user an instant response “{0} meets all your requirements”. But Cofman doesn’t stop here, they also provide another result “{1} houses meets nearly all your requirements” giving the user with a lot of preferences a second chance to find a house.

See it for yourself. Watch the video or go the cofman.com homepage.

remember the milk has this great ajax enabled signup process:

Especially pay attention to the way the Username is validated as you type with the text “{0} is not available”

Dave Ward has an ASP.NET AJAX username availability check implemented with ASP.NET and AJAX UpdatePanel.

Daves implementation it not, like the one rememberthemilk, working with key down but checks the availability when the control lose focus.