S23.org do the trick for me. Every now and then I get pinged that translatewiki.net has gained a few places in the ranking of the largest MediaWiki wikis.
Currently at number 48, there are only 4 Wikia wikis and Wikihow in front of translatewiki, the rest are Wikimedia Foundation wikis.
When you follow the activity, translatewiki will continue to rise in these rankings. With no bots editing, it is a triumph for the localisation of the supported projects.