Folks:
Forgive the commercial, but I suspect this will be of interest...
Maik Schmidt has been working behind the scenes to produce "Enterprise Integration with Ruby," a book that looks at the ways Ruby can be used to create new enterprise functionality by gluing together existing enterprise resources. He looks at databases (both relational and LDAP), Xml processing, low-ceremony networking (sockets and HTTP), high-ceremony networking (SOAP, RPC, etc), and tools.
It's a great book (I know I learned a bunch from it), so we decided to release it early as a beta book: buy it and get the PDFs as Maik works on it. If you opt for the paper book, it'll ship as soon as it's ready. As with all our PDFs, updates are free for the lifetime of the edition.
There are more details at http://pragmaticprogrammer.com/titles/fr_eir
Enjoy!
Dave