thoro: you have a retired Silicon Graphics ?! Damn.
My system (all second-hand at best…) : Dell Optiplex G1
PII/350MHz
256MB RAM
8GB + 20GB, CDRW
Philips 17" multimedia monitor
Running Linux debian sid and KDE 3.3 (or WindowMaker, depending on my mood).
Actually two :D. When I updated my desktop PC it became so much faster that I switched.
But these Silicon Graphics workstations are really cool. I always dreamt of getting an SGI, and some day at work we needed a unix workstation and I asked my manager for an O². I also ordered Lightwave 5.6 to do some 3D work on it but Lightwave was so instable on this machine that I looked for another solution. The year was 1998 and I discovered Blender - the interface seemed very strange but it was easier for me to learn than Lightwave and it was running just fine :D. When I left the company I bought the machine.
Give that computer some clothes - no naked computers around here please!
I might as well chip in as work is a bit slow today 
Main PC
P4 2.4ghz, 1gb RAM (PC3200), 128mb GeForce 5200FX, 120gb SATA, 80gb ATA
(other bits - DVDRW,CDROM,SBLive! audio card, Emagic Audiowerk2 audio card, 1 x 17" AOC TFT monitor and 1 x 14" Dell TFT monitor)
Laptop
Sony Vaio (Can’t remember the model but I think it has X18 in it)
P3 600mhz, 128mb RAM, 10 or 15gb hard drive and no idea what gfx card.
Going to upgrade soon, but here are the specs:
Antec lanboy case.
16x Microtek DvD reader
24x10x40x lite-on writer
60 gig maxtor (ugh! don’t buy maxtor)
40 gig western digital.
Wind0$e Xp
Gentoo Stage 1.
Geforce 4 mx440 with massive 2 slot heat sink for when I overclock (haha, slow card otherwise)
Game Theater XP 6.1 w/breakout-box
rtl8139 nic
AthlonXP 2400+ thoroughbred
I think that’s it…
pentium 3 450mz
128 ram
6 gb hd
8 mb video card
windows me