Listed here are a number of Harry Potter and related reference sites. If a site is listed here, it's because I consider it to be an exceptionally good resource for the serious Harry Potter fan. As a rule, I don't trade links or place web sites here on request. I choose the sites to place here because I think they're the best.

If you want a good link page with plenty of fan sites listed as well as links to news articles, check out Sirlinksalot's Harry Potter page or this excellent list of reviewed sites from the University of Wisconsin's School of Education.  But if you're doing research and want good, well-written and presented information, you can't do much better than the sites listed here.

If you're looking for where all the facts in the Lexicon came from, check out "Sources of Lexicon Information".

Selected resources

Other Potter encyclopedia sites:
Hogwarts Haven
extensive character lists and pages devoted to each house
Webrary's Harry Potter Guide
from The MGPL Webrary, very nice short encyclopedia of people, places, and things
The Harry Potter Guide
this excellent site  includes lists of spells, characters, locations, and much more - one of the best Harry Potter sites on the web
Harry Potter Facts
Here you can look up a name, term, etc. and find concise listing of where it is found in the books.
Sadly, The Encyclopedia Potterica is no more. Jenna has taken  down her site, The Unofficial Harry Potter Fan Club, and the Potterica with it. If anyone knows how to contact Jenna and can put me in touch with her about this, please let me know!

Etymology, pronunciation, and name sources
What's In A Name? - etymology resource for names, words, and phrases in HP 
Harry Potter: Pronunciation Guide - gives pronunciations for tough HP words 
The Akashic Record - very thorough listing of spells, names, etc. from the Harry Potter books,  with eymological information and other facts
Latin Word List - great resource for Latin roots
Encyclopedia Mythica - the premier web resource for mythological references
The Ancient World Web - excellent index of mythology & religion web resources
Harry Potter Pronunciation Table - gives pronunciations for many, many HP words
Do You Know Mundungus Fletcher? - meanings and associations for HP words
Dictionary of British English - from Arabella Figg's Hogwarts Express website
Dictionary of English Slang and Colloquialisms of the UK - very complete
CJVLang Site - This fascinating site explores the challenges of translating the Harry Potter books into Asian languages

Creature references
Mythical Creatures - non-HP reference site

Reviews and discussion
Harry Potter's Magic - by Alan Jacobs, a wonderful analysis of the magic in HP
Harry Potter for GrownUps (HPfGU) - best Harry Potter discussion group on the web, designed for adult fans of the books - most of the contributors to this Lexicon are also active members of HPfGU.

News and related information
The Leaky Cauldron -  The best HP news site on the web, hands down.
MuggleNet - A wide variety of information, news, and activities for HP fans
Snitchseeker.com - Fan site with a lot of excellent content and current news
The Restricted Section - Another excellent fan site, not the least of which because of the very fine encyclopedia pages

Interviews with Rowling
collected interview sites
Talking Jo - Searchable database of Rowling interviews
MuggleNet's interview archive

individual interviews:
on Scholastic.com, February 3, 2000 (Sch1)
on Scholastic.com, October 16, 2000  (Sch2)
on Barnes & Noble.com October 2000 (BN)
on AOL October 2000 (AOL)
on Comic Relief website 3/12/01 (CR)
on Southwest News 7/8/00 (SN)
on BBC Newsround 27 April 2001 (Nr)
on BBC Newsround 2 November 2001, aboard the Hogwarts Exress (HE)
on BBC Newsround 19 September 2002 (NR2)
with Raincoast Books March 2001 (RC)
on CBC Radio's This Morning, October 23, 2000 (CBC)
with the Houston Chronicle, March 20, 2001 (HC)

Interviews without transcripts (so far)
"J.K.Rowling--Harry Potter and Me," 28 December, 2001, BBC1 (HPM)
on Blue Peter TV show 3/12/01 (BP)
Q&A at the National Press Club, October 20, 1999 (NPC)