Atari 1040 STE (needs keyboard fixing)
Atari Mega STE (4MB, HD floppy)
UltraSatan SD card interface that works with both the above
C64 Breadbin
3 x 1541-II drives - but only one working PSU at the moment
MMC Replay -
another SD card interface
Oodles of cartridge-based games
800+ floppy disks waiting to be imaged up!
Spectrum in a DK Tronics keyboard
Spectrum 128 +2 x 2
Divide interface - OK, not SD, but Compact Flash interface ;-)
1 x Sega Saturn (Japanese model with Multi-Region BIOS)
2 x Gamecubes (1 modified, the other not)
SD Launcher device
Dreamcast (UK and Japanese models)
SNES (with Multi-Region BIOS c/o porchy and a SNES Everdrive). I also have a Double-Fighter Pro device - but it's still packed away somewhere.
N64 (USA model with a collection of pristine N64 NTSC & Japanese boxed games)
Chinese bootleg Megadrive (with Everdrive MD)
Xbox (with a proper chip and a 120Gb h/drive)
2 x briefcases full to the brim of Xbox 'homebrew'
1 x large box full of Xbox originals too (over 100 and counting).
PS2 - With network adapter and using HD Loader and a approx 60 or so original games.
PSP - Custom Firmware v3.30 with a 16Gb memory cards
PSP - Same as above but with a 4Gb memory card which is Eleanor's.
Approx 50 or so original games which will be sold off at some point.
Amiga 4000 (almost forgot that one!)
Atari Jaguar
I'm sure there's loads more but this is just off the top of my head for now