The gridselect module adds a new form type that displays content in a similar way to facebook friend pages (specifically the pages you see when inviting friends to events).
Sometimes when working with large database generated sites, or administrating large user-generated content sites you can end up with hundreds of empty taxonomy terms and tags.
Service Attachments is an framework that allows you to find information related to nodes on YouTube, Flickr, Wikipedia, ... You can extend it to add your own services.