Yes, this post comes late, but in case you missed it: Austin Appleby has released a new version of MurmurHash 2, optimized for 64-bits CPUs.
MurmurHash is nothing but the fastest hash function ever designed so far. It’s a non-cryptographic function, but it has excellent distribution, excellent avalanche behavior and excellent collision resistance. Plus, it is public domain.
Speedwise, MurmurHash beats Bob Jenkin’s lookup3 hash and Hesieh’s Superfasthash hands down.
and of course, there’s already a Ruby extension: Ruby extension for MurmurHash 2
Might make a PHP one if I ever have time to waste.