[dottrap]

Also there is the header-only khash.h [3], complete with benchmarks:

https://attractivechaos.wordpress.com/2008/08/28/comparison-...

(Also provides kbtree.h, ksort.h, kstream.h, kvec.h)

[3] https://attractivechaos.wordpress.com/programs/

Also there are the stb header-only libraries. There is a hash table implementation buried inside stb.h

[4] https://github.com/nothings/stb