Edit: everything is sold. Thanks!
Here's a rough list of the kind of stuff that's here. Many systems have multi-carts and have various mods such as video and enhanced controls. Pictures at the end.
Intellivision 1 & 2 with cuttle cart 3
7800 with s-video mod
MSX 2
C128 with matching disk drive
C64 with two disk drives and multi-cart switchbox
Coleco Gemini (stock)
Coleco Adam with spare working tape drives
Colecovision with component video mod and Adam expansion module, custom controller with port to connect Atari/Genesis controllers and still use the keypad.
Generation NEX NES with wireless and wired controllers
Jaguar with CD
Atari 65XE with SD flash drive loaded with games
Atari ST with monitor
TI 99 4/A with VGA mod
Mattel Aquarius (stock)
Dreamcast with VGA box
PS One (stock)
Gamecube with region switch, GBA player, hori classic controller and two wavebirds
Amstrad PPC640 portable DOS PC for retro DOS games.
Sega Nomad
Atari Lynx II
GameGear with Master System Adapter
Master System with s-video mod
Vic-20 with multi-cart adapter (tons of games too)
Nuon with games and several controllers
Atari 5200 with s-video mod, masterplay converter modded to allow use of Atari 2600 paddle (for Kabooom!) and to work with two of the buttons of a Genesis controller. Includes several multicarts with games you can't buy.
Turbo Duo with brand new laser
Super Nintendos with s-video and GameBoy adapter
Two Saturns with action replays
Sega Genesis with region switch + 32x
Pile of 2600's
Activision Branded 2600 with ROMscanner multi-cart switcher
X68000 with VGA cable - Capcom 6 button controller adapter, keyboard, mouse.
PS2 with HD loader and games on HD
Virtual Boy
Vic20 multicart
Odyssey 2 multicart
Vectrex multicart
Tons of ColecoVisions
Lots of 2600, 5200 and Atari 8-bit games on cart and disk
Tandy CoCo 3 with 512K RAM expansion, IDE interface and Compact Flash adapter.
Various RGB monitors
Atari 2600 demo kiosk parts with working motherboard, some artwork and controls.
Apple II GS with RAM expansion
Arcade "SuperGun" with a few games.
Lots of arcade motherboards but nothing too exciting - unless you like really obscure stuff.
Lots of DoubleJump strategy guides
Lots of other stuff I haven't dug out yet.
Tons and tons of misc.