Besides the documentation article Slava linked to, you might find this blog post helpful: http://rethinkdb.com/blog/async-drivers/

If there's anything else you think is missing from the documentation that would be helpful, open an issue here: https://github.com/rethinkdb/docs

We're still working on the full documentation for the Twisted and asyncio backends. We'll put it up in the next days. You can find the Tornado documentation under the link coffeemug mentioned.

Take a look at this -- http://rethinkdb.com/docs/async-connections/