Tips for tweaking your kernel.
If you remove things you dont need from the kernel, like SCSI support if you dont have SCSI devices and wont ever want to use a USB Mass Storage device such as a Digital Camera, you end up with a smaller kernel - which will in turn boot faster. I've not measured how much benefit you get from this however
There are a number of patches around at the moment to reduce latency or provide realtime support for Linux. This is a fairly dynamic field at the moment and the best way to keep up to date with this is to go to http://lwn.net and search for realtime or latency.