I gave a rather short webcast on 2/3/2004 on some fundamental principles of interoperability, regardless of platform or technology. You can see the webcast here.
Note that I say this is a rather short webcast - this was really my fault. I was having so much fun blabbering on and on about interop principles that I ran short on time. I was still able to sneak in a quick demo of BizTalk and a look at BEA WebLogic Workshop (I even snuck in a plug for BPEL). I'm working on a paper as a follow-up that will include a more detailed look at these development platforms.