Translatewiki.net has supported the Babel extension for a long time now. Practically everyone who contributes has this information on their user page and the projects someone contributed to is added as well.
The big advantage of the Babel extension is that it works without templates and that new messages are available every day with the LocalisationUpdate.
Several projects have requested the implementation and, when Babel becomes generally available, it will be easy to add relevant information on the user page without the painful copying of a zillion templates.
With the implementation scheduled for September 21th, this is surely happy news.