I saw that Google had a nice proposal/standard for making Ajax applications crawlable, via #! (hash bang).
http://googlewebmastercentral.blogspot.com/2009/10/proposal-for-making-ajax-crawlable.html
My questions are:
It appears to me that this is more than just a proposal - that Google is already using this protocol.
I found more info here. They have enough docs and FAQs on the subject that refer to websites actually being crawled this way already...
It's only a proposal so it's not being used yet (at least no one has announced it as being used but it is not uncommon for search engines to keep their capabilities a secret. At least for a little while).
It's hard to say if other search engines are going to use it but if it is standardized the odds are they will as they have been lock step with other standardized functionality (nofollow, etc.). Typically proposals take a while to be discussed and agreed upon (i.e. HTML 5) although it is always possible someone (i.e. Google) unilaterally implements it and the others are forced to adopt it simply to keep up.
I don't know a fully Ajax compatible crawler atm. But is has enough crawlers/bots who are specialized on reading JQuery, Prototype and other frameworks. Also some proposals and "quick&dirtie" solutions for ("good") refactored JavaScript are on the way to be stable. Just search on Google Code. I don't know if it is a good idea to post some links here.
Btw: Most Ajax websites are fully crawable because many Users uses AddOns like NoScript to deactivate JavaScript. So most sites provides a fallback solution. (also for old browsers).
As an update, this protocol is fully supported now on Google. However, Bing does not support the protocol at this time.
