AJAX seems to be a very popular feature on websites. I was curious as to how many WordPress themes are AJAX-enabled. Here is a 4 Ajax Enabled Free WordPress Themes
White theme with 2 columns, right sidebar, dropdown menu, ajax comments driven by jQuery
Stylish WP Theme with a boxed CSS layout and an ajax sidebar brought to you by Neuville.
It has in-built ajax comments which requires no extra plugins to be uploaded.
A light blue theme with rounded corners, ajax, and gravatar and widget support