My DripDrop framework for zmqmachine/EventMachine just saw a whole bunch of ZMQ improvements, it now supports PUSH/PULL and XREQ/XREP in addition to PUB/SUB sockets. Also, the ZMQ handlers have been completely refactored to be much cleaner, making adding additional socket types much easier.

http://github.com/andrewvc/dripdrop

Checkout the examples folder for usage.