Via OSNews, I was reminded of ActiveOberon (now renamed to BluebottleOS. ActiveOberon is a member of Oberon family with built-in concurrency support. Its language report (html) is also available as pdf.
Interesting thing about Oberon is that it's not just a language but OS as well from its first day. So far ETH and other instituions made several OSes eg V4, System3, Native Oberon and Bluebottle.