Streamlined is a framework that sits about Ruby on Rails and makes developing Rails applications even quicker than possible with scaffolding alone. It includes a ton of useful stuff like pre-built layouts, a REST layer around all the models, support for Atom, and its own DSL. As developer Justin Gehtland explains:

Streamlined is an open source framework for quickly creating data-centric applications with Ruby on Rails. We've been using Rails and Ruby to build applications for our customers for going on two years now. Over time, we've realized that, like in just about every development platform before, we spent a lot of our time building and rebuilding the same stuff. Over time, we started pulling out the commonalities until we discovered we had the makings of a framework. Streamlined is the result of that. We want to take the redundancy out of building apps and let us (and you) focus on the things that make our apps different.

Streamlined is not yet released but should be made available in July at OSCON. I'll be posting again when this happens.

This is a great demonstration of how extra projects can extend the ease of use and power of Rails without Rails needing to adopt every new idea directly. I envision many different Streamlined-esque 'quick application generators' appearing over the next year all focused on different niches and feature sets.