Fresh from the clogged tubes of teh intarwubs…
"This post serves as a collection of useful tutorials on working with AJAX in a wide variety of ways. You’ll find tutorials on working with forms, building shopping carts, creating chat features, working with log-ins and usernames and much more." Yup.
"Some post-related data is not available to get_posts by default, such as post content through the_content(), or the numeric ID. This is resolved by calling an internal function setup_postdata(), with the $post array as its argument."