Image Store
WordPress plugin: Image Store (ImStore) is a photo gallery and store plugin with Paypal and Google Checkout integration. You will not find any extra tables in your database (Cool!.. I hate extra tables ).
File Un-attach
WordPress plugin: This plugin will allow you to detach any file from any post, but it will also allow you to attached any file to multiple post. It aslo has suport for the wordpress gallery shortcode.
Popular widget
WordPress widget: Display the most commented or most viewed posts in a tabed widget, filter the post by date range or by category. It also includes a tags tab. It supports custom post types.;