I can make this quick. AJAX and SEO do not mix. Search engines can not read AJAX, because most search engines won't read most JavaScript. So when you implement AJAX, make sure to give search engines alternative methods of getting to the same content that is accessible via the AJAX form.
There was a nice presentation given at SES Chicago 2006 named CSS, AJAX, Web 2.0 & Search Engines where Jim McFadyen from CriticalMass gave some nice tips and examples of AJAX and alternative solutions implemented right and wrong.
He loves Amazon's Diamond Search feature.
JavaScript turned on - i.e. AJAX version:
JavaScript turned off - i.e. non AJAX version:
This shows an example of how Amazon is using an alternative to JavaScript for their users. But a search engine won't be able to index and crawl Amazon's non-AJAX version, because it is using image maps, forms and so on.
A good alternative would to design a linked based alternative that somehow has some of these filtering options.
Forum discussion at High Rankings Forum.
