Since GParted does not support RAID, what tools can we use to create a RAID drive (0,1,5 etc) and then install Ubuntu onto that drive? Assume we are starting on fresh system with no OS.
I am assuming you mean Linux Software RAID rather than hardware RAID.
The alternate CD supports installation onto a Linux Software RAID setup. Here's a link to a screencast I made showing how to do it.
Alternatively you might want to try the new palimsest disk utility on the live CD as this has some options for configuring Linux Software RAID.
It is also possible to install on Linux Software RAID using the Live CD and the mdadm utility. Boot from the Live CD and then "sudo apt-get install mdadm" which is the tool required to create the RAID setup. You'll need to use fdisk (or gparted) to create the partitions and then mdadm to create the RAID array(s).
There are plenty of guides to using mdadm online.