Ifaraone points at a good tutorial for this. If you're used to RedHat kickstart, the Ubuntu approach will probably annoy you to begin with. Don't be tempted to use the Ubuntu "port" of kickstart config - it's insufficiently mature at this stage to be flexible enough.
In particular, disc partitioning using preseed is a real pain, as the partman configuration "language" is obtuse, under-documented and insufficiently flexible. It is, however, possible using techniques similar to those documented at http://blog.loftninjas.org/2007/07/04/complex-lvm-on-an-alternative-install-of-ubuntu-debian-installer/ to rip partman out and do your own partitioning in a script. Recommended if you want to do anything quite so unusual* as running LVM on top of software RAID.
Once you've got preseeded network installs running, I'd thoroughly recommend looking at using puppet for managing configuration from installation onwards.