I am in the midst of creating a "learnscape" for an organizational initiative. While analyzing the current situation and trying to design one that has more of a collaborative "component" embedded in it, I found myself asking this question. Preliminary research did not yield very satisfactory answers. Looking forward to your responses...
My view is that they are essentially the same thing; although I do believe they operate within a slightly different context. My sense is that a CoP is a group that collaborate with the specific objective of collaborating to discover excellence; whilst a CoE is a group that collaborate with the specific objective of collaborating to spread excellence. So it's largely a function of how well excellence is understood at this stage of the domain's development.
I can't imagine a CoP whose objective isn't to determine excellence!
For me, one is the intention (CoE), the other is the practice (CoP). COP enables CoE. Effective collaboration is integral to success. The exchange of ideas, knowledge, experiences in a forum that folks can tap into and operationalize is critical to productivity. I dare to say, if you don't have quality CoP in place, you're not likely to have quality CoE either. Just some thoughts from across the pond. '-M