D20 Go

Publisher's blurb: D20 Go is a complete roleplaying game streamlined for asynchronous play-by-post but still complete enough to be played around the tabletop. Inspired by older editions of Dungeons and Dragons, D20 Go is flexible enough to let you create any kind of character and any kind of fantasy story you want. The core rulebook includes everything you need to play. Roleplay anywhere, any time.