Gregor Hohpe, of ThoughtWorks has published live a number of enterprise integration/messaging patterns, including Message Routing patterns, Message Transformation patterns, and System Management patterns. The pattern site is currently a work in progress, more patterns will be added.

They can be found here. The site was published a couple of months ago.

You can also read them in published form from the submissin to the PLOP 2002 conference.

from the site:
The patterns presented on this site help integration architects and developers design and implement integration solutions more rapidly and reliably. Most of the patterns assume a basic familiarity with publish-subscribe messaging architectures. However, the patterns are not tied to a specific implementation. Most patterns apply to EAI suites as well as Web Services or JMS-based applications. In some cases, a pattern may already be embedded in the middleware package. This is a sign that the vendor recognized the recurring problem and incorporated the solution into the package. We still present these patterns for two reasons. First, not all packages implement the same patterns, so a user working with another package will still find the pattern useful. Second, despite the default implementation of the pattern in the middleware package, a description of the forces and alternatives is insightful for any architect or developer who is interested in EAI concepts beyond the specific package implementation.

good work,it would be more readable if u can change the font for the contents in the site...

It seems to me that a lot of the work that these patterns are doing would be better modelled within a workflow system.

Kyle Brown, of IBM, had a paper that was submitted at Plop on Messaging Patterns. Both papers complement each other well.
http://jerry.cs.uiuc.edu/~plop/plop2002/final/woolfbrown2.pdf

here is the link

I particularly like the doodle language. Fills a gap between UML and largely useless high level architecture diagrams.