Fortitude is a new rendering engine for Ruby (with or without Rails), based on the same principles as Erector. It expresses HTML using a Ruby DSL. By doing this, it allows you to factor your view layer far more (and much more naturally) than any other templating engine, allowing dramatically better maintainability and code quality — in what is often one of your application's largest layers.
Currently, Fortitude is in beta release: while there are no known bugs, and it has extensive tests (548 examples and counting), it is as-of-yet largely undocumented and has not received much use outside of its author's environment. As a result, it is largely intended for people who are already familiar with Erector, and for use in environments where occasional bugs (that will be fixed quickly) are not an issue.
Fortitude should be production-ready in a short while, including very extensive documentation.
If you're familiar with Erector and want to use Fortitude, see README-erector.md.