I am learning this also...
Some great suggestions from KC... even for an Apple guy....

Seriously... I have Redhat 9 ...4 discs if you include the docs...
But I would also suggest you download one or more of the LIVE CD's
Mepis would be my first choice... Knoppix is also fun...
These are great because you get to play with different distro-butions without having to install them... They boot and run in RAM... Autoconfigure to your hardware etc...
They are much more up to date than RedHat 9...
Newer kernels, newer desktops and more...
You can test drive both KDE and Gnome desktops
They have open office, cd buring software and more...much much more...
The first thing I learned is that with Linux, access to the internet for downloads and updates is critical...
Oh, and Winmodems dont work well in Linux.. obviously...
(So checking your hardware compatibility with the Live CD's just makes sence)
Oh and there are alot of people fighting problems with the Nvidia chipset right now..
Pure luck... I was running ATI...
I run 98se, XP and Mepis dual boot
I have been working on some custom Live versions for different things like data recovery on Windows systems...
Boot to a CD run an OS in RAM and have access to Windows files...