Oh boy... lotsa systems here...
Stuff I owned at the time they were hot:
(1983-1990) C64, C64c, 1581, multiple 1541s and clones, Skyles IEEE / SFD floppy drives, buffered serial interface, etc...
(1990-1992) Amiga 500, sidecar HD (Dataflyer+RAM)
(1992-1994) A1200, GVP 030 JAWS Series 1 @ 40mhz.
(1994-Present: retired to retro duty around 1999) A4000, CSMKII 060 @ 50mhz, CV64-3D, Ethernet. -- (Currently the CSMKII isn't functional :-( It's still my very favorite Amiga, though, so eventually I'll either cough up the dough for a CSPPC or ship the CSMKII to Amiga Center France for repairs.)
(1999-2003) AMD T-Bird 900mhz (later upgraded to a OC'd 1100 mhz after a cheap processor swap), GeForce 2
(2003-Present) Pentium 4HT 3.0C (800fsb), added GeForce 6800 GT/OC in 2004 -- (My current main system)
(2003-Present) PocketPC -- HP iPaq 4155 (Can run PocketUAE and PocketCommodore64, which I HIGHLY recommend.)
Noteworthy Cool Stuff I accumulated well after it's heyday:
SGI Octane R10k / SSE (Wicked crazy system - replaced the faulty incandescant front panel with cold blue LEDs)
SGI Indigo 2 R4400 / Extreme (Bright Teal!)
A1200D / GVP Series II 030 (Feeling nostalgic about the one I sold to afford my A4000)
SX64 (Luggable C64 Goodness - currently needs some work)
NOS A500 (Thanks, Red!)
A3000 (Used to run a friend's BBS - currently needs work)