Design your own Domain Specific Languages and plug them into Java easily. Think of all the business rules, workflow definitions, structured configurations or handy language extensions that you could simplify your life with. Using purely open-source tools and without defining a parser or grammar.
JetBrains MPS gives you that and more - textual and graphical languages, non-parseable and tabular notations, tight integration with Java and full IDE assistance on top of it - the ability to edit, debug, refactor, test and analyze your DSL code right inside a Java IDE. If you're thinking of trying something new, this session is for you.