Note: If you currently own Don't Starve on Steam, you will get Don't Starve Together for free when it exits Early-Access. By purchasing the Frontier Pack, current owners get Early-Access, and a bonus copy for a friend.
http://store.steampowered.com/app/322330/?snr=1_7_15__13
For more information and FAQ check out our roadmap here: Don't Starve Together Roadmap