Google Code Blog: Introducing Closure Tools
Closure Compiler is a JavaScript optimizer that compiles web apps down into compact, high-performance JavaScript code. The compiler removes dead code, then rewrites and minimizes what’s left so that it will run fast on browsers’ JavaScript engines. The compiler also checks syntax, variable references, and types, and warns about other common JavaScript pitfalls. These checks and optimizations help you write apps that are less buggy and easier to maintain. You can use the compiler with Closure Inspector, a Firebug extension that makes debugging the obfuscated code almost as easy as debugging the human-readable source.
This, and the other tools, look awesome.