So I have a laptop that I've been upgrading since Hardy (currently on Karmic Alpha) that I would like to boot faster. It has probably accumulated a lot of crufty daemons along the way that probably aren't being pre-loaded into memory. I picked up this tidbit from the fast boot expert. Add profile to your kernel command-line (at the grub prompt, press Esc e and then edit the line). This will update your system's readahead file list after a lot of disk churn. On my machine, it sped up boot by only about 5 seconds, but YMMV.
Also, if you have a machine or netbook with SSD (flash) disks, sreadahead might give you a boost. Again, apt-get install sreadahread is your friend. sreadahead also schedules profiling of the system every month-or-so, so it keeps those boot-essential programs in the readahead cache always.