4. F#

F#, a Microsoft language is designed to be both functional and practical unlike pure functional languages, Lisp and Haskell. 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.

Somewhat similar to OCaml, F# has numeric data types that 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.

F# ships with Visual Studio 2010 with the compiler and core library available under the Apache open source license.

5. Opa

Opa proposes 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. This is done through a combination of client- and server-side frameworks. The Opa compiler decides whether a given routine should run on the client, server, or both, and it outputs code accordingly. For client-side routines, it translates Opa into the appropriate JavaScript code, including AJAX calls.

Opa's runtime environment bundles its own Web server and database management system, which can't be replaced with stand-alone alternatives. Opa is open source and available now for 64-bit Linux and Mac OS X platforms, with further ports in the works.