Is it feasible for you to cite some popular open-source ESB?
SCJP 1.4, SCWCD 1.4
Joined: Jun 30, 2003
There are lots of popular open source ESBs.
What we see however is that the two most popular at this moment are Mule and ServiceMix.
And new interesting one though which has recently gained a lot of attention is Spring Integration.
Probably the easiest ESB to get started with is Mule. It provides a low entry level, very powerful ESB. If you're interested in a JBI compliant ESB to get started with ServiceMix is probably the easiest.