There is Pore
Pore is a plugin for the up-and-coming SpongeAPI built to provide compatibility for Bukkit plugins on the platform. Please note that this project is still under heavy development and is not yet considered functional. Currently, no Bukkit plugins are verified to be supported.
but it is even less functional then Sponge currently is, and is not related to the Sponge project, so help for running bukkit plugins on Sponge should be asked on their thread.