Just over a week ago, I picked up a 2006 revision 20" ACD. To go alongside it, I've installed a fresh copy of Tiger on my 17" MBP. I also put my 20" iMac G4 next to it. Not an Intel machine, but looks great next to it.
I've decided to make this a 2006/2007 only machine, making it a time capsule into what the Mac looked like during the early stages of the Intel transition. Other than TenFourFox Intel (of which I may end up compiling InterWeb for 10.4 Intel, either using the G5 or 10.6 codebase, if possible?), it's only running software that was out at the time, such as iLife/iWork '06, CS3 and FCS2.
I also have my 2007 Mac mini sitting underneath the ACD to raise it up to my eye level, and have my 13" MBP underneath the 17". So that makes 4 Macs on this desk (excluding my rMBP).