Xtext is an awesome open source framework for programming languages and DSLs covering all aspect of language development.
The final result is a full feature development environment integrated with Eclipse including syntax highlighting, code completion, quick-fixes etc.
For those interested to became familiar with XText I recommend the book by Lorenzo Bettini, Implementing Domain-Specific Languages with Xtext and Xtend.
To make it simple, we created a short video to introduce the GAPE DSL. Hope you enjoy it.
The link to the GAPE SDK download is available on here.
You can become familiar with GAPE by playing with the GAPE's Anatomy available on the demo application.