Beginning Google Maps Applications with Rails and Ajax is a book by Andre Lewis, Michael Purvis, Jeffrey Sambells, and Cameron Turner that, simply, looks at how to develop Google Maps powered applications using Rails. You can read some sample chapters from the very-similar PHP edition (sorry!) on the official site.
The authors are running a free prize draw for at least 3 free copies of the book, and entries must be in by midnight on March 14th Eastern Time. They call it a 'contest' but you don't have to actually do anything other than fill in your name and e-mail address, and they actively support you passing the link around so all your friends can enter too (unless they happen to work for Apress).