In October 2009, Google proposed a way to index AJAX. Back then, all it was, was a proposal, but it was not implemented. However, last week, Vanessa Fox reported that the AJAX feature for Google is now live and well.
I am not going to get into the technical details of how it works again. In fact, you can read about that over here and begin implementing it as soon as you like. We currently have no real feedback on how well it works yet, so I will keep my eyes open on that in the forums.
However, Vanessa Fox did see signs of Google crawling AJAX earlier this year and wrote up some of the pros and cons related to that.
In any event, I may want to give this a try myself on some of our sites and let you know how well it works or not.
Forum discussion at WebmasterWorld.