2.6 kernel with critical components compiled in (not as modules) could speed things up a bit.
I'd also check your hdparm settings (make sure dma is on, 32 bit blah blah).
Make sure you're not running any services you don't need.
Try switching off swap. This may or may not do anything useful (and I await flames for suggesting this) since you've got plent of RAM.
Umm, that's all I can think of just now.