Gone - An ephemeral to-do list
Friend Hunt - Get desktop notifications when your friends comment on PH
Streaks - The to-do list that helps you form good habits.
#MakerGoals - Live Twitter embeddable GIFs of your Product Hunt stats
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
History of Product Hunt - Learn community building from Product Hunt's example