If you like talking about TV but hate spoilers, you're going to love TV Yapp™.
Track the shows you and your friends are watching and the episodes seen.
Create chat groups by inviting friends who have seen the episode you wish to discuss.
Include friends who are watching the show but are behind you. They won't receive any messages until they catch up. Once they do, they can join the discussion and not miss out on what was already said.
Keep the same group together and discuss the next episode with a push of a button. No need to wait for others to watch or worry about spoiling anything. Just spill your thoughts and your friends will only see them when they're ready.
Search for people nearby who watch the same shows you do. Maybe meet that special someone who's down to re-watch all 121 episodes of Lost with you.