I came across a post on Warner Onstine's blog; he's working on a book on DSLs for the Pragmatic Programmers. Sounds like a great project; and I'm glad to see that they're including a chapter on what are usually known as "external DSLs" with ANTLR and JavaCC.
He has a comment about how well PragProg's book production system is working. I used what I think is a similar system - Docbook plus a bunch of customized XSLT and Ruby utilities - to put together Generating Parsers with JavaCC and it's worked out quite nicely too. It's great to be able to run all the code examples and have both the code and the output plugged into the book's content - no more copying and pasting code! I was even able to do callouts, which I only used in one or two places, but it's handy to have the option.