Any good translation platform as engine (or as saas)?

Hi, I need to translate in a crowdsourcing way my website. While ago I
tried Tolk (https://github.com/dhh/tolk) which is nice, but I'm looking
for something else.

Is there anything like the Twitter platform (
http://translate.twttr.com/welcome )?

Something with ranks, eventually gamifications and stuff like that. In
order to give [real] prizes to the best translators. Something directly
integrated (as an engine) would be better, otherwise a saas which permit
single sign on access in order to use (and track) the existing user
accounts

Thanks!