Which distribution were you installing - Ubuntu, Kubuntu, Edubuntu, or Xubuntu? In Ubuntu/Edubuntu/Xubuntu, reiserfs is definitely offered - you just have to delete the filesystem and create a new one, which is a bit odd, but there you go. I don't have Kubuntu to hand to check.
Which distribution were you installing - Ubuntu, Kubuntu, Edubuntu, or Xubuntu? In Ubuntu/ Edubuntu/ Xubuntu, reiserfs is definitely offered - you just have to delete the filesystem and create a new one, which is a bit odd, but there you go. I don't have Kubuntu to hand to check.