If you made it all the way to the end of this book, you probably have developed some level of fondness for Rails. Nonetheless, you may find that Rails is more than you need, not quite appropriate for the work you want to do, or otherwise annoying. You may even want to supplement your Rails application with something written using a different framework. If you’re interested in exploring further, these are a few of the available options:
A very minimalist piece of middleware, more of a web server interface, that mostly provides a way to connect servers with other Ruby frameworks. It implements a simple direct connection to HTTP requests, and supports handlers that connect to different web servers, letting you switch servers however seems convenient.
Rails 2.3 will actually use Rack as its foundation, and will likely offer "Rails Metal", a toolkit that lets your Rails applications include quick and tiny bits of code that run without all of the overhead of Rails routing and Action Controller. If your application includes functionality that needs constant polling, for example, the performance savings can add up quickly!
Originally Mongrel plus ERb, Merb started out as a simple tool for supporting file uploads alongside Rails, but developed into a very different framework. Merb provides a few packages for key things, but the basic gem is deliberately minimal. There is an object-relationship manager, ...