Code.Org is a very huge open sourced project. It has 689,577 words in total with 259,418 words translatable. It's aiming for 76 languages to go global. I am one of the contributors to help with Chinese Simplified translation.
Here's link of the translation that I've done for them-
https://crowdin.com/project/codeorg/activity_stream
I completed 544 words.
Before and after progress-
Posted on Utopian.io - Rewarding Open Source Contributors