I have been interested in CORBA right from the beginning (i.e. when the standard was so embryonic, CORBA would not even interoperate with itself!). Despite the complexity of the standard, I still think CORBA has a lot to offer. I have used several ORBs, some open source, some proprietary. My favourite used to be MICO but unfortunately the support for multithreading is still not finished so TAO (the ACE ORB) is now the winner. I have also looked at JacORB by Gerald Brose.

The best proprietary ORB (IMO) still seems to be Orbix from IONA (now owned by Progress).

For those interested in CORBA I recommend heading over to the web site of Ciaran McHale, a former IONA consultant whom I have worked with before. He has a free book there which I think provides a great practical introduction to programming with CORBA.