this tutorial will show you how to set up a multi-head system in most linux distros, primarily ubuntu. please note, this is still largely unfinished.
Step 1: Install Your Hardware.
the title explains it. i'm assuming you know how to open the case and install the cards. just make a note of which card is where and which monitor is on which card. FYI: my system uses one Nvidia riva tnt2, one nvidia riva tnt, and one 3dfx voodoo3. (in that order on the pci bus)