Clipman-plugin
sudo apt-get install xfce4-clipman-plugin
No config function. No hotkey. Very basic function. But it support 1-step-paste.
Parcellite (1.0.2rc5)
Installation with apt-get is different with that with Software Manager. That from apt-get seeams working strange, so not use it. Use Software Manager to install it. A GUI and you can config its hotkey. But its a 2-step-paste app (you have to select a item using hotkey, then focus target text editor, then ctrl-v to paste). Parcellite can enable "copy on selection" by checking "Use Primary" and "Synchronize clipboards" in [Preferences -> Behavior -> Clipboards]. So it's unnecessary to install Terminator, because this feature of Parcellite is more powerful: selection in both GUI and console can be auto-copied to clipboard.
Glipper (2.4)
Install with Software Manager. Behave like Parcellite, you can configure hotkey, but 2-step-paste.