The concurrent by default paradigm looks like it could be really useful for some cases. Does anyone know of any more well-used languages that support it?
As I mentioned in my other comment Verilog and VHDL are "concurrent by default" since that's how hardware works anyway.
If you want to experiment with them you don't need an FPGA, you can just start with a simulator such as Icarus Verilog[1] and a waveform viewer like gtkwave[2] and get a feel of the language. There are a bunch of tutorials on the net.
It's a "well-used language" in academic contexts, but probably not exactly an answer to your question ;) Anyways, in OZ[1] you can just add thread <x> end around code x, and it's concurrent. It will wait for all bindings to be resolved before continuing.
It's a pretty cool language with a lot of paradigms one can easily try out.
If you want to experiment with them you don't need an FPGA, you can just start with a simulator such as Icarus Verilog[1] and a waveform viewer like gtkwave[2] and get a feel of the language. There are a bunch of tutorials on the net.
[1] http://iverilog.icarus.com/ [2] http://gtkwave.sourceforge.net/