"Post-Modern" Computer Hardware Scene:

• Jim Bagley's PropGFX system
• Chris Smith's Harlequin project - ZX Spectrum in discrete logic
• Dennis van Weeren's Minimig project - Amiga on a FPGA
• C-One: A super-charged Commodore 64
• Arcade machines put on a single chip
• CPC TREX - A seriously souped up Amstrad

Retro graphics:

• Mark's Pixel Art tutorial

Computer / Console software emulation:

• Spectrum: (Emulators), World Of Spectrum (software etc)
• C64: WinVice (emulator), "C64.com" (software etc)
• Amiga: WinUAE (emulator), Some legal game downloads.
• Megadrive: Gens (emulator)
• Snes: Snes9x (emululator)
• Arcade: MAME (Windows GUI version emulator link)

Computer "museums":

• Old-computers.com - Excellent - Very comprehensive.
• Oldcomputers.net - More US-centric but also good.

8 Bit Nostalgia:

•  C64HQ - Interviews with C64 coders / musicans etc
•  Lemon64 - Loads of info on C64 games etc

Retro remakes:

•  Retrospec - Game remakes
•  Remix.kwed.org - C64 SID music remakes

Modern demo scene:

•  Monostep.org
•  Scene.Org