Professional Ruby on Rails Developer's Guide: Driving Rails Into the Enterprise, by Obie Fernandez, coming out early 2007. The book aims to be a definitive nitive Rails reference work for professional Ruby developers in the enterprise. It features proven advice about Rails adoption in the enterprise, insights derived from real-world experience, and an in-depth reference section about the Rails APIs and the most useful Rails plugins available.
The Ruby Way: Solutions and Techniques in Ruby Programming, Second Edition, by Hal Fulton, coming out Fall 2006. The bok is a "how-to" practical reference guide to the Ruby programming language. The second edition has been updated to cover the latest features of the Ruby language and the arrival of Ruby on Rails.
Performance Rails: Building Rails Applications with Sustainable Performance, by Dr. Stefan Kaes, publishing in Spring 2007. Stefan Kaes is an expert in high-performance Rails scalability; he shares his wisdom about how to benchmark, configure and tune production Rails applications to achieve optimal throughput and fast response times. See also the the Common Rails Performance Problems article on InfoQ by Stefan.
Also upcoming in the next couple of months from Addison-Wesley are short for-pay PDF downloads called 'shortcuts', the following three Ruby titles are in the works:- Mongrel: Serving, Deploying and Extending Your Ruby Application
- Rails Plugins: Extending Rails Beyond the Core
- Rubyism in Rails