Yann Collet (known for the LZ4 compression algorithm) has now updated his xxHash algorithm with a 64 bit version, and it's speed is quite excellent. On my machine, a 64bit MBP @ 3GHz:
xxHash64 - ~13.5 GB/s
CityHash128 - ~12.5 GB/s
CityHash64 - ~11.5 GB/s
MurmurHash3_x64_128 - ~5.5 GB/s
The XXH64 is implemented mainly for 64 bit platforms, so it's performance is not as good on 32 bit systems. But then you probably would use XXH32 anyways.
I'm sure more tests will reveal more of the hash quality in the future.
For code and speed comparisons, check it out at https://github.com/Cyan4973/xxHash