Feedir - Feedir makes it easy to find job listings on Twitter.
crewmap - Helping everyone find a best friend at work
Nicetweeps - Discover the nicest tweeps based on your interest
Surf - A simple web browser based on WebKit2/GTK+
FriendZone - Make new friends based on your interests and hobbies
Bartiqo - Connect with people with the same professional interests.