(Common) Lisp fits your bill. It's threadable, cross-platform, compiles to machine code, well supported, stable, and able to be molded to any domain (such as web development). In fact, there are already some great web/app servers and frameworks for it already.
It's not "highly popular" compared to something like Python, but has growing usage and attention. The implementations are converging on a standard set of modern features that are cross-platform. I routinely write code in one implementation/OS and run it on different implementations/OSes without a hitch.
>It's not "highly popular" compared to something like Python, but has growing usage and attention.
Let's not kid ourselves. CL will never get anywhere regarding adoption for web use (at least for values of "never" = in the next 20 years, and "anywhere" = several high profile companies use it, and there are at least 3 dedicated books about its web frameworks).
Almost all programming languages can claim "growing usage and attention", but it rarely amounts to much. Go has managed to have more usage and attention from high profile companies in 3 years of existence that CL or Smalltalk have had in the last 25.
It's not "highly popular" compared to something like Python, but has growing usage and attention. The implementations are converging on a standard set of modern features that are cross-platform. I routinely write code in one implementation/OS and run it on different implementations/OSes without a hitch.