HFS+ resize

[Matthew S-H]

Hey guys.  I got another problem.
I just got a new iBook.  My last computer was a 4-5 yr old Dell PC 
running WinXP, Ubuntu, Debian (seperately from Ubuntu), and Gentoo.
Anyway, I wanted to install Ubuntu on this computer.  The only problem 
is that I can't reformat the hard drive (too much data would be lost).  
Anyone know of any partition magic type tools that are compatible with 
HFS+?  I just need to downsize the partition to fit a ext3 partitions.

~Matt