ZeroMQ Guide has frequently been mentioned on HN as one of the better pieces of software documentation:<p><a href="http:&#x2F;&#x2F;zguide.zeromq.org&#x2F;" rel="nofollow">http:&#x2F;&#x2F;zguide.zeromq.org&#x2F;</a><p>It is useful not just for using ZeroMQ, but about learning about distributed systems in general.