Ajax and like techniques have great potential to make web site user interfaces more responsive, but there is potential here to conflict with architectural principles of the web http://www.w3.org/TR/webarch/. In particular, the relationship between a URI used to access a web page and the resource whose state is displayed should not be violated. Note that when a user interacts with a page using Ajax (or similar techniques), the URI of the displayed page does not change, so the underlying resource should similarly be maintained. The exact nature of the relationship between a URI and the corresponding resource is subject to considerable debate, but a useful touchstone might be: if a page using Ajax is bookmarked at any stage during a user interaction, can the URI thus obtained be used to retrieve something clearly related to what is displayed when the bookmark was saved? -- GrahamKlyne
Does modifying the URL in the address bar as the user navigates count? Is this possible? What about providing links in the page to bookmark?
http://www.adaptivepath.com/publications/essays/archives/000385.php (Google snippets this as "Seminal article which popularised "AJAX" as a term")
http://www.javaworld.com/isearch?qt=AJAX&x=0&y=0&site=javaworld&ms=1&tid=1&st=1&rf=0 javaworld articles on AJAX
http://www.onlamp.com/pub/a/onlamp/2005/06/09/rails_ajax.html - introductory article on rapid developent of Ajax applications with Ruby and Rails
http://www.xml.com/pub/a/2005/02/09/xml-http-request.html an article using PHP on the server side
http://rajshekhar.net/blog/archives/85-Rasmus-30-second-AJAX-Tutorial.html - Rasmus' 30 second AJAX Tutorial - a "learn by doing" example
http://ajaxpatterns.org/Main_Page - has some articles covering more advanced Ajax techniques.
Some other links (not yet checked):