Cut and Paste
Xorg's environment lets you copy and paste text with Ctrl-C to copy the text and Ctrl-V to paste the text. If you want to remove the text when copying it then you can cut the test using Ctrl-X instead of copying it with Ctrl-C.
parcellite is a great lightweight GTK+ based clipboard manager which works on all desktops. This lets you keep a large selection of previously cut/copied text which you can later choose from. You can even edit the clipboard directly and later paste the text.
klipper is a KDE clipboard manager with a few more features. It can be used in other desktop environment too, even Gnome.
Clipboard-managment does not always go so smoothly
There are a few issuese with both these clipboard managers. They do NOT support advanced elements. This means that you get crap instead of actual results when copying parts of spreadsheets in LibreOffice. Klipper likes to fill memory and use a lot of CPU and bug a whole lot when copying images in image programs like GIMP.
Temporarily kill the clipboard-manager when using LibreOffice or other software which wants to use the clipboard for advanced things.