F# has a huge chance to get a lot of people who are interested in Haskell or OCaml, however. I love the language, but having to deal with Mono is not fun (it's tolerable, but not fun) - so I look forward to the day when I have an officially supported toolchain and CLR implementation to use it outside of Windows.
Apparently some releases of F# already work on Mono: http://www.mono-project.com/docs/about-mono/languages/
And there's also a CoreCLR branch: https://github.com/Microsoft/visualfsharp/tree/coreclr
If anyone is interested in helping out, there is also a wiki page on how you can help port it to CoreCLR: https://github.com/Microsoft/visualfsharp/wiki/How-to-help-w...
Personally, I'm a huge fan of the ML-style syntax, in JVM land there is Frege but I'm less a fan of the full purity approach it derives from Haskell (I don't care how easy you say the IO monad is to work with, it drives me batty and I like to consider myself a pretty smart guy).
Type providers, excellent async support out of the box, active patterns, there's a lot of great features in F# as well that make it worth looking at.
... and OCaml: http://www.ocamljava.org/
Does anybody know what are other cmunities (ruby, python, nodejs..) up to an what is happening in their ecosystems?
That just isn't the case anymore, and might just have saved Microsoft's platform from slowly becoming Lotus Notes/Domino or something.
A lot of ASP.NET 4.x is open source, e.g. ASP.NET MVC and ASP.NET Web API.
I've actually been running an ASP.NET site on a Linux machine for a few months using just all of their open source stuff. Works pretty well!