is an agile and dynamic language for the Java Virtual Machine builds upon the strengths of Java but has additional power features inspired by languages like Python, Ruby and Smalltalk makes modern programming features available to Java developers with almost-zero learning curve supports Domain-Specific Languages and other compact syntax so your code becomes easy to read and maintain makes writing shell and build scripts easy with its powerful processing primitives, OO abilities and an Ant DSL increases developer productivity by reducing scaffolding code when developing web, GUI, database or console applications simplifies testing by supporting unit testing and mocking out-of-the-box seamlessly integrates with all existing Java objects and libraries compiles straight to Java bytecode so you can use it anywhere you can use Java
This is a very interesting presentation by Werner Vogels, CTO at Amazon.com: The Amazon.com Technology Platform: Building Blocks for Innovation. Amazon's Dynamo technology is also very interesting. I suspect someone could build a very lucractive consulting practice by specializing in just Amazon Web Services. Add to that: SalesForce.com's Platform capabilities; and Sun's Grid Computing Utility.