These are either individual collector's sites or references to jump-off points for other collecting sites and activities. All sites open in their own windows.

Kevan's Computer Collection - my old host's own collection site.
Steve Cooper's collection page
Rhode Island Computer Museum
Heimcomputer.de
Stefan Walgenbach's Home Computer collection
Jim Trageser's computer page
Obsolete Computer Museum
Thomas Hillebrandt's site - Thomas is a Danish collector with an understanding girlfriend :)
Old-Computers.com - great site from France stuffed with machines and information. The 4 owners have over 1000 machines between them!
Didier Luthi's own collection, nicely organised!
Erik Klein's personal collection, complete with a web-based forum.
Flash's collection site, home to a working Tandata PA.

Retro Gamer - a new UK newstrade magazine dedicated to Retro Gaming, Remakes, Emulation, Classic Hardware and Software

Woz.org's Mac Links

Rich Harding's Dragon32 repository
Simon Hardy's Dragon Archive
Bo Zimmerman's Commodore collection
The Enterprise Repository
Cameron Kaiser's Secret Weapons of Commodore
The Nascom 1 homepage
Ultimate Play The Game appreciation website
Memotech MTX Memories
MTXWORLD - Memotech resource page
Jim Wills' Memotech page, by the man who founded Megastar software
MTX Computer Site by El Senator
Jag's House of Old Macs
Mick's Nascom Pages - get yer Nascom answers here!
AtariClassic - home of a few thousand unopened classic carts
AtariAge - excellent Atari history site
Apple-History.com is a great source of info on Apple kit
LowEndMac is also a great source of info on Apple kit
AppleFritter - Tom Owad is collecting info on every Apple clone out there!
Steve Marshall's Oric site, dedicated to Tangerine's little offspring
Famiclone.emucamp.com - Excellent site stuffed with Nintendo Famicom clones
Ian Matthews' excellent site chronicling the history of Commodore and its products.