Etsy and Twitter's Engineer Exchange Program

Twitter and Etsy are working together on a new project to help their engineers learn from the others’ practices, with the idea of making both engineering teams better as a result. "We hope to learn what makes each other tick, how we celebrate our successes and learn from our failures, and how we can each be better in the end"

This emphasis on cross-pollination of ideas and practices should extend beyond tech companies, and I think it's a pretty cool model to generalize.