Oh, sorry I missed that. Well you'll need a LiveCD (or that's the easiest way) for this; I guess most if not all of the common LiveCD distributions (like Knoppix) include partitioning software, like
gparted (for Gnome) or
qtparted (for KDE). With those you can resize reiserfs, and I suggest you download the Ubuntu 6.06 LTS normal installation/LiveCD that you can use (besides installing) as a normal LiveCD distribution. It has gparted partitioning software on it, and it's easy to use. That way you don't need to mount your root partition and can resize it.
Gparted's features table:
http://gparted.sourceforge.net/features.php
So, what you do is:
1) Go to
www.ubuntulinux.org then open the "Downloads" page, pick up a location near you and download the "Pc (Intel x86) desktop CD" which you can use as a LiveCD
2) Once you've burned it on a cd-r (or cd-rw if you plan to reuse the disc later), boot from it and run Ubuntu live session
3) I think it's in System menu (if not, then look in Applications or launch it from a console), so open up
gparted
4) make sure the partition is not mounted: open up a console and issue
mount command (or if you like,
df command), and make sure your root partition isn't there in the list; if it is, issue
umount to the root partition.
5) Select your root partition from gparted's list and click the Resize button
6) Choose how much you want free space
7) Commit changes. I've encountered a situation where I was unable to commit changes when I had done multiple things (resized, created new partition etc.) so you better commit changes after each step, so it works
8) gparted probably asks you if you're sure. Sure.
9) Use gparted to create your new partition, if you like. Remember to commit the changes before quitting.
That's about it. Then just reboot..