Equally important, Go is meant to be easy to program in. Its basic syntax is C-like, but it eliminates redundant syntax and boilerplate while streamlining operations such as object definition. The Go team's goal was to create a language that's as pleasant to code in as a dynamic scripting language yet offers the power of a compiled language.
Go is still a work in progress, and the language specification may change. That said, you can start working with it today. Google has made tools and compilers available along with copious documentation; for example, the Effective Go tutorial is a good place to learn how Go differs from earlier languages.
Experimental programming language No. 4: F#
Functional programming has long been popular with computer scientists and academia, but pure functional languages like Lisp and Haskell are often considered unworkable for real-world software development. One common complaint is that functional-style code can be difficult to integrate with code and libraries written in imperative languages like C++ and Java.
Enter F# (pronounced "F-sharp"), a Microsoft language designed to be both functional and practical. Because F# is a first-class language on the .Net Common Language Runtime (CLR), it can access all of the same libraries and features as other CLR languages, such as C# and Visual Basic.
F# code resembles OCaml somewhat, but it adds interesting syntax of its own. For example, numeric data types in F# can be assigned units of measure to aid scientific computation. F# also offers constructs to aid asynchronous I/O, CPU parallelization, and off-loading processing to the GPU.
After a long gestation period at Microsoft Research, F# now ships with Visual Studio 2010. Better still, in an unusual move, Microsoft has made the F# compiler and core library available under the Apache open source license; you can start working with it for free and even use it on Mac and Linux systems (via the Mono runtime).
Experimental programming language No. 5: Opa
Opa doesn't replace any of these languages individually. Rather, it seeks to eliminate them all at once, by proposing an entirely new paradigm for Web programming. In an Opa application, the client-side UI, server-side logic, and database I/O are all implemented in a single language, Opa.