KDE ships with Klipper by default, while Gnome has no built-in alternative. Though I prefer a little history, the absence of a clipboard manager isn’t the worst thing in the world. However, xclipboard forgets what you copied if you close the application from which you were copying, which is a serious annoyance and a usability issue for new as well as seasoned Ubuntu users.
Luckily the situation is easy to rectify.
sudo apt-get install glipper, right-click on a panel, click “Add to Panel,” select the entry named “Clipboard manager” and click “Add.”
If you want to paste something other than the currently active copied text you can either select it from the Glipper icon or, if you prefer a more keyboard-based approach (like me), you can press Ctrl + Alt + C to pop-up a list of available items. Of course you could change that keyboard binding to anything you like.
The default settings are fairly sane, so unless you want to keep more than the last 20 copied items in memory you can leave it be.