In KDE there is an option where the user can configure the double tap on the touchpad for emulating the third button. Then the user can open new tabs in Firefox or paste the content selected on the terminal just using a tapping with two fingers.
However, I did not find this option in XFCE (Xubuntu 14.04). I've seen the solution suggested for XFCE running on Ubuntu 12.04, but it does not work in my case.
Any suggestion?