Built around helping "friends and fans socialize and share experiences around live events," Hot Potato is a social networking site based on events added to a calendar. Then, add friends and invite others to join you. Use Hot Potato to discuss the event and ask questions before it happens, and share thoughts and photos afterward. At first look I wondered if we really needed another social networking site, but it's a great service for events from professional conferences to the next episode of your favorite TV show. You can tweak the settings on the site to view comments from everyone or just from friends — a great way to tap into new thoughts and ideas.
Its just-released iPhone app makes it easier to use Hot Potato to find and participate in events near you while on the move. And the service is integrated with all of your other networking sites (including location-based sites like Foursquare), making it easy to find and keep up with friends.