Xubuntu (Xfce 4.10) and Dell 3100cn (CUPS)
CUPS.og: Dell Laser Printer 3100cn Driver
openprinting.org: Dell 3100cn
Add Printer -> Network Printer -> Dell Laser Printer 3100cn -> Forward
No Drivers found -> Select PPD -> dl3100.ppd -> Change from Letter to A4 -> Done!