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!