I currently have two PC's running on Fedora 12 and I am quite enjoying the experience. Now I am considering running them dual boot with Ubuntu 10.04. Is this possible?. My first inclination is to run them on different hard drives but it seems do wasteful and awkward. I was also thinking of external hard drives but again my expertise level on computers leaves me groping in the dark for answers. Any answers would be greatly appreciated.

Hi, there is no problem at all running two distros side by side. However, you do need to create a new partition for the root filesystem (using two different drives would amount to the same thing). the beauty of Linux (and any other UNIX) is that if your /home is on a separate partition, the two distros could share it, thus you would have all your documents in the right place (home directory) and even most of your config might be the same ("might" because sometimes distros change the default directories).
External drives would work too, but your PC would have to support booting from USB.

Is there a link to a site which would explain how to set a partition. I enjoy Fedora but it is a learning process for me and it is going slowly.

If you have a big hard drive and at least 2gb of memory, you can install and run Ubuntu in VirtualBox. Just another option you could try. Fedora would be the host and Ubuntu the guest.

both ubuntu and Fedora have quite nice graphical partition managers, so only basic understandig is enough (ie what a partition is). For a little more advanced knowledge try wikipedia. (some of the linked articles also provide a good read).
If its just for the sake of trying out ubuntu, I agree with Fred in that you should simply run it in a virtual machine. again there are many options : Xen, Virtualbox, KVM (kernel virtual machine) and maybe one or two others.