Are you going to be destructively or nondestructively partitioning
your hard drive? By destructive, I mean starting from scratch.
Nondestructive means keeping your existing data intact and shrinking
the existing partition(s).
If destructive is ok, then just use the partitioning program included
in the installation of the distribution you choose.
If you want to do it nondestructively, by far the easiest and safest
program is Partition Magic. However, it will set you back about $70
(although it is worth it, in my opinion, if you want to do anything
more then the bare minimum).
http://www.ranish.com/part/ is a good free program that can be run
from DOS. I've never had it screw up, but it has a steep learning
curve.
QTParted is included with knoppix. It has a gui and so is slightly
more intuitive the ranish partition manager, but just doesn't "seem
right" to me. In other words, I feel more comfortable with ranish,
even if it took longer to learn.
I think Mandrake may be able to nondestructivelty partition also, but
I'm not sure.
The main reason to use partition magic is it can handle many more cases
then either of the free ones. Often times, Windows 2000 and XP will
put files toward the end of your parition, and not move them when you
defrag. (I've run into this on more then one computer). ranish and
QTparted being merely partitioning programs won't move data, and so
can only shrink as far as the last data in the partition. Partition
Magic is much smarter and will move that data, and allow you to shrink
as much as possible.
My advice is to leave the free space unpartitioned, and then use the
partitioning tool included with your distribution to partition the
free space.
PS All major distros (and almost all others) include partitioning tools. Very few include nondestructive partitioning tools, though.