Eight months ago the WordPress.com image carousel made its debut. That first iteration of the carousel made it possible for an image gallery to display a set of thumbnail images attached to a particular post or page. The gallery shortcode could also be used to display the post or page’s gallery. Now the improved version 2 of the carousel is avaliable to WordPress.com users and to WordPress.org users via the Jetpack 1.5 with Carousel plugin.
If you haven’t yet to discover this excellent resource on working with galleries in WordPress.com blogs then do yourself a favor and visit Random Acts of Photography AKA Not The Official WordPress.com Gallery FAQ. It’s been updated and contains the answers to almost every carousel and gallery related question you can ask.