World Of Spectrum : The biggest Spectrum archive of all, containing emulators and almost every single game released.
The Tipshop : The largest collection of hints, tips, hacks, cheats, maps, etc for Spectrum and SAM games. Literally thousands of entries for thousands of games!
Your Spectrum Unoffical Archive : Jim Grimwood has built a site dedicated to Your Sinclair's predecessor, Your Spectrum. On the site is many many articles from the two-year series of magazines and comes very highly recommended.
Crash: The Online Edition : The site which does to Crash what I did to Your Sinclair. A top collection of Crash articles.
The ZX Spectrum Reviews Database : Astonishing site which contains ALL CRASH reviews!
SUMO - Sinclair User Magazine Online : ...and an equivalent site for fans of Sinclair User!
Planet Sinclair : One of the original Spectrum nostalgia sites. Lots of articles and information on everything related to Sinclair products.
Sinclair Research : The legendary company lives on.
comp.sys.sinclair FAQ : The FAQ for the comp.sys.sinclair newsgroup.
ZX Format : If you want to know what's happening in the Speccy scene, whether you're emulating one or using the real thing, then ZX Format magazine is for you.
RetroSpec : A team that has acheived God-like status through their game remakes on the PC (and other machines). Check out their Skool Daze/Bak To Skool remake called Klass of '99 and be AMAZED! And then there's always their utterly incredible Head Over Heels remake too...
YS3 : YS was the original Your Sinclair magazine, YS2 was the "interesting" tape mag that came on the cover of the later issues, and here's YS3, a Spectrum retro-mag that's written in the style of YS, and hits the YS atmosphere and feeling right on the nail. Well worth a look.