Startups and companies in social media that are working on a list-based concept. To be clear, this list of companies do not include sites that have purely editorial lists.
Still in stealth but supposedly a tool to facilitate creation, sharing, and correlation of lists. Founded by Dave Morin of Facebook and Sean Fanning of Napster - probably the highest profile startup in the list space.
A place to list, rate, tag and review movies, TV shows, music, games and books. Does not have any close integration with Facebook or Twitter. Lists are not reordered based on crowd feedback.
Dinevore’s list-based approach to restaurant recommendations incorporates historical, intentional, professional and social data to give you the broth you want.
TwtPick.in makes lists easy and social. It is currently integrated closely with Twitter and helps folks leverage their Twitter graph to produce interesting lists. It is evolving into a tool that bloggers and publishers can use to better engage with their audience.