Banking systems, both retail and commercial. Logistics. Embedded. Clusterware. Telecoms. Robotics, AI. When it comes to messaging, don't forget RabbitMQ and all the SMS systems.
For those of you who don't now, Francesco Cesarini is the founder and CTO of Erlang Training and Consulting, and has been a major proponent of Erlang for years, also having co-written the book "Erlang Programming" (http://oreilly.com/catalog/9780596518189 - it's a great book, I highly recommend it myself)