There are some Linux modified scheduler on Internet.
The best one for general purpouse application is QNX-like scheduler patch from Adam McKnee (firstname.lastname@example.org). It is a patch for kernel 2.0.32.
I am testing the performance of this scheduler for a University exam and the preliminary results says it is better than standard one .
It would grant good interactive performance under heavy CPU load.
You can find the patch at www.linuxhq.com or by contacting the autor.
Hope this helps