Languages:
Java/Groovy, Ruby/jruby, C/C++, Perl, SQL/plpgsql,
VXML, CCXML, Javascript/Coffeescript/TypeScript, Scala, Python, Clojure, php, golang
Frameworks:
Spring, Grails, Rails, Lift, Play, Twisted/Zope, node.js, Zend, Meteor
UI: Angular 2, React
Mobile: Android, Cordova, Meteor Mobile, Ionic
Appservers:
JBoss, Tomcat, Jetty
Middleware:
Camel, Akka, RabbitMQ, ActiveMQ, Redis, MongoDB, Memcache,
Big Data: Kafka, Storm, Zookeeper, Graphite, Kibana, Elasticsearch, EMR, Hadoop
Tools:
SIPp, Sipper, Jenkins, Cruisecontrol, junit, ant, gradle, maven, git, svn, make/bison/flex, Puppet
Protocols:
SIP, HTTP/S, HEC, RTP, H.323, MRCP, AMQP, JMS, DNS, SNMP, TCP/IP, WebRTC, TLS, Websockets...