Confronted with some integration work, I was looking around for an opensource ESB solution, with a community and enterprise version at a reasonable price-range. Previously I followed openESB by SUN, but the project died in 2010 after the Oracle deal. At some stage ESB was very popular with consultants as the silver bullet for integration problems. The crowd moved on (to cloud computing as consultancy topic), the dust settled and you can have a serious look at the remaining products out there. Have a look at Wikipedias summary. Having only Apache Camel and Servicemix left on my list I came across MULE ESB.
Getting my hands dirty with MULE configurations, I get the hang on it and quite like the product ! Lots of transports and connectors, a good documentation and recently they added visual (eclipse based) IDE to create flows.
I still recommend to learn the configuration “language” first to understand the underlying concepts. I will share some of my experiences and sandbox activities here.