I recently scored a TON of hardware from Facebook Marketplace, with 7 different computers (1 Dell Dimension 3000, the rest were system builder PCs). 6 Of these system builder cases were from 2000-2004, and all of those are beige. All had motherboards, not all had RAM or hard drives, but most did, all had CPUs, all had video cards, CD drives (some even two, of course all are beige except for the Dell), floppy drives, you name it, I got it all for USD $40, and all hardware from this find will be noted with an asterisk. Systems with cases used from this find are listed with a pound symbol.

I'll list the specs of these builds here:

[Pentium III 500# Build]
Intel Pentium III 500MHz
Intel WS440BX Motherboard
128MB PC100 SDRAM
3DFX Voodoo Banshee AGP*
Creative Labs Soundblaster Live! Value
20GB Maxtor 2B020H1 5400RPM IDE HDD
48x16x48x IDE CD-Writer (Placeholder until Creative 52X IDE CD-ROM* is restored)

[Pentium III 1000 Refresh]
Intel Pentium III 1GHz (Placeholder for Celeron 1100 for fastest @ 100MHz FSB)
Gateway Bryant i810e Motherboard
256MB PC133 SDRAM (Running as such until 100FSB is introduced, for some reason separation between chipset/memory frequency does not work here)
3DFX Voodoo 3 2000 PCI* (There is intake and a non visible small but high RPM fan as exhaust in the case, and a 120MM Fan is pointed directly at the Voodoo 3 both over the chip and VRM)
AOpen AW744L-II PCI
[No HDD at the moment, waiting for ~20GB IDE HDD]
52x32x52x IDE CD-Writer (Placeholder until 8X IDE DVD-ROM is added)

[Pentium 4 2.4# Build]
Intel Pentium 4 Northwood 2.4GHz, 533FSB*
Intel D845PESV (Perfect capacitors!)*
512MB PC2700 DDR
nVidia RIVA TNT2 32MB AGP (Placeholder for Radeon 9500 PRO 128MB AGP that is on the way)
Creative Labs SoundBlaster Audigy 2 PCI
40GB Western Digital WD400 7200RPM IDE HDD*
48x24x48x LG IDE CD-Writer*

[AMD Athlon 64 3400+ Refresh]
AMD Athlon 64 3400+ Venice (S939) 2.2GHz, HT 800
Gigabyte K8NF-9 Motherboard
1GB PC3200 DDR
nVidia GeForce 6800 256MB PCI-E
Realtek ALC850 Integrated
250GB Seagate 7200RPM SATA II HDD
Sony CRX320E IDE CD-Writer, DVD-ROM*

[Intel Pentium 200 Refresh]
Intel Pentium 200MHz
QDI P5I430TX Titanium IB+ Motherboard
32MB 168-Pin 60ns EDO @ Fastest Stable Timings
Matrox Millenium 2MB PCI
Creative Labs SoundBlaster Vibra 16s (Yamaha OPL 262)
1.2GB Seagate Medalist 5200RPM IDE HDD
Packard Bell GCD-R580B 8X IDE CD-ROM*

I have a planned build and planned refresh, of which I have most of the parts to:

[AMD K6-2 400MHz# Build]
AMD K6-2+ 550ACZ @ 400MHz 66x6
PCChips M570 (SiS 5591) Motherboard
64MB PC-66 SDRAM
nVidia RIVA 128 4MB AGP* (or if RIVA 128 doesn't like 5591 AGP: Matrox Millenium II 4MB* OR S3 ViRGE/VX 4MB)
[OPL2 ISA Soundcard Needed]
4.3GB Samsung SV0432A 5400RPM IDE HDD
[CD Drive yet to be selected, Likely no name 52X CD-ROM*]

[Intel 486 DX2-66 Refresh]
Intel 80486 DX2 66MHz
IBM PC 350 Socket 3 Motherboard
16MB 60ns EDO
Cirrus Logic CL-5430 1MB ISA VLB
[Riser card to be inspected with multimeter and sealed if OK, OPL2 ISA Soundcard Needed]
IBM 540MB IDE HDD
[CD Drive yet to be selected, likely a spare CD-Writer as my 486 didn't like the no name 52x drive]