However many of the libraries list under "third party" are either unmaintained or not really ready for production. The stuff in the standard library seems pretty good though (although I've not used Nim for serious production work)
Except it's nothing like that, it's like an interpreter framework written in Python with a reference implementation that happens to be a Python interpreter. Write your interpreter in RPython, use the right decorators and boom you have a compiled interpreter with a free JIT (with speeds that beat C in some workloads, apparently).
http://nim-lang.org