I'm working right now on creating a service that operates on messages with javascript.  The service is java and javascript makes a natural choice since almost everyone has to use javascript these days for that pesky web development. 

I'm using the Rhino package from Mozilla.  Right now I'm very impressed with the ease of use of this package. 

The main driver behind this is processing plain text.  Plain text just can't be changed to XML via XSLT.  So obviously a nice scripting language could manipulate the message to add tags and parse for naughty characters that XML doesn't like. 

I will post on how this turns out.