Fortress (http://en.wikipedia.org/wiki/Fortress_(programming_language)) and X10 (http://en.wikipedia.org/wiki/X10_(programming_language)) were the other two languages that came out of the DOE HPCS program (http://en.wikipedia.org/wiki/High_Productivity_Computing_Sys...) that might be interesting if you liked Chapel.

Other aiming-for-HPC languages include co-array Fortran (http://en.wikipedia.org/wiki/Coarray_Fortran) and Unified Parallel C (http://en.wikipedia.org/wiki/Unified_Parallel_C).

I never really saw any of them while working in HPC, though. It was just Fortran, C, and sometimes Python. The Python would really just call out via SWIG to a C function for the numeric kernel.