miniblog.

LLVM's lit tool for testing files is the most successful testing DSL I've ever seen. It's used a decent number of projects outside of LLVM. By contrast I don't see many folks using e.g. Cucumber these days.

A thorough introduction to Rake, including a good discussion of why you might want an internal DSL on top of Ruby rather than a custom language like Make:

The line between 'full-blown DSL' and 'full-featured library' is extremely fuzzy. I find it hard to use 'DSL' in a clear, meaningful way.