Official Paramount site - not the most complete official site in the world, but there's still an episode guide, cast bios and a small gallery to check out

TheWB - the WB's own website has a section devoted to Charmed.

WB11 - the WB affiliate in New York has a section of its website devoted to Charmed (contains spoilers for UK viewers).

Channel 5 - Channel 5 now devotes a section of its website to the series (and it's better than Paramount's)

LivingTV - as well as the usual stuff, Living's Charmed site has a rather bizarre design and gets Paige's surname wrong!

Planet-SF provides a portal to Angel, Buffy, Charmed, Doctor Who and Roswell sites plus mailing lists for all these series plus Alias and Dark Angel

Planet Buffy - online since January 1999 with Buffy and Angel news, features and reviews

The Crash Festival - Roswell news, features, reviews and episode guide

The White Room - the Planet-SF forum

Charmed-UK - talk Charmed with over 100 fellow fans, with a two-tier spoiler system for LivingTV and Channel 5 viewers (non-UK viewers are also welcome)

Transdiffusion - the largest media history site on the web, including some articles by yours truly!