But I will also give you a quick go-over of all the diffirent most popular official ubutnu family OSs:
Standard Ubuntu: Linux for Human Beings Using the Gnome Desktop Enviroment. A fork of debian made to be more 'human oriented'
UNR(Ubuntu Netbook Remix): Ubuntu for netbooks. Whih is what us and I love it! Note: Don't use the default netbook desktop, it uses up too much cpu. Just switch to the deafualt one, add gnome-panel and gnome-wm to the startup apps and voila, much better (if you want the netbook window effect, you just need to play around a bit with the toolbar!)
Ubuntu Server Version: Ubuntu for Server Machines (I you don't know what a server is, Look it up!)
Xubuntu: Make with XFCE which makes it better for old computers. It is very fast for old computers so don't trash you're oldies, just but Xubuntu on em!
UMR(Ubuntu Moblin Remix) An ubuntu version of Moblin(Mobile linux) I don't know much about it but please comment on this post to tell mee what it's like.
Gobuntu: A 'Green and Free' Version of Ubuntu. I think people are too crazy about green and natural so i don't agree with the philosophy of this one!
Mythbuntu: An Ubuntu for 'Myth TV'(I dont have a clue what that i)
Kubuntu Netbook(October09): Kubuntu 'Netbook Remix': Coming out in the future and i sure hope it's good!
An there are probably half a million others (Macbuntu, H...) but they are so small(and much probably worse), that I do not add them to this post!