It is my understanding that NUMA (Non-Uniform Memory Access) is a kernel feature. As long as a distro supports the newer 2.6.x kernels, NUMA support is included. There are set of patches for the 2.4.x kernels that adds this support, but I wouldn't want to mess with that personally.
That being said, NUMA won't do much (anything?) for you unless you have multiple memory controllers connected to different CPUs (Dual-Opterons with memory connected to both CPUs for example.)