People and organizations are doing a lot of interesting things with Mozilla technologies. Here are two of the many Mozilla-based applications available. If you would like to suggest other applications to feature, please leave a comment.
Instantbird is a multi-protocol Instant Messaging client that uses the Mozilla rendering engine and the Pidgin libpurple. Using it, you can connect to all your different IM accounts.
Snapstick combines the ease of discovering content on your laptop, tablet, or smartphone with the viewing pleasure of a big screen TV.