What are the new language choices for Experienced programmers?

I know the topic I started is too subjective. But I just wanted some expert guidance learning new languages. I've been working with .NET languages (C#, VB.NET) quite a few years (around 4). And it's been years since I stopped experimenting with new laguages after settling down in a job.

Few weeks back I just started working on my personal project, which I am going to spend much time in the coming months. During the analysis I found that I just can't accomodate the luxuries of cost effective languages, programs and IDEs. So I planned to move to the wide spectrum of open source languages and tools.

And when I look at the current choices, I was just speechless. Hundreds of promising open languages and toolsets and I found it's hard to choose. And I can't even think of evaluating each language myself (it's a worst nightmare). Currently I started with Mono (for the sake of C#).

I felt this is going to be a good chance for learning new programming languages and models. So I am open to any language that offers me the following:

more functional
dynamic language features
better language elegance (like lambdas, Haskel like SQL syntaxes or C# LINQ)
better community support
must be open
easy interaction with the web
support for parallelism and concurrency (easy threading)
better in performance
proven web frameworks
better IDE support (I got this ease of use syndrome after using years of MS tools)

I love the Haskel and Erlang language programming approach. But I don't have a clue about these languages' web stack and concurrency mechanisms.

EDIT: i would appreciate few reasons along with your choices. It will be really helpful.

Solution

I think that all these meet your requirements:

My bet is that you'll get the groovier IDE experience with Groovy (and it's Groovy Eclipse Plugin).