DebianAdministration.org has another excellent and simple guide to get your Debian to boot faster (that one time each year you have to boot it).
As they mention it in the article:
Several people have written guides on booting Debian systems faster. Most of these involve reordering initscripts, and other significant changes. There is a much simpler alternative to speeding up boot times though, whilst it might not work for all it's an interesting hack.