Appraisals
NAIFA
The Appraisal Foundation
Appraisal Institute

Brokers

BOMA.org
Buyer's Agents
National Association of Exclusive Buyer Agents
REBAC - Real Estate Buyer's Agent Council
Commercial
International Council of Shopping Centers
National Association of Industrial and Office Properties (NAIOP)
Building Owners and Managers Association
CCIM Institute -  Commercial Investment Real Estate
CPN Online
Institutional Real Estate, Inc.
SIOR - Society of Industrial and Office Realtors
Counselors
CRE The Counselors of Real Estate
Educators
IREM Home
The Real Estate Educators Association
Government
Fannie Mae
Federal Reserve
Freddie Mac
Ginnie Mae
HUD

Inspection

American Society of Home Inspectors
 

Designations and Certifications

I've removed this list because it was far from complete, and had little relevant information. 
Here is a better list:
Real Estate Certifications and Designations

General Information Sites

RealEstate4 - Comprehensive directory of Real Estate related sites
Real Estate Investing Depot
Real Estate Supply
Real Town

Discussion Groups

ActiveRain Real Estate - A Real Estate Network of which I am a member.
Agents Online
CRE Online
DealMaker's Cafe
Everything RE
George Paukert's Real Estate Forum
Knowledgeplex Discussion Boards
NARS, Creative Real Estate Discussion
Open Real Estate Investor Forum
RayComo'sHouseBuyingKingdom
Real Estate Discuss
Real Estate Forum @ BayHouse
Real Estate Forums @ DoItYourself
Real estate investing discussion forum
Real Estate Investing Main Message Board
Real Estate Link Forum
Real Estate Talk - MAREI
Real Estate Talks
Real Estate Webmasters
Real Life Real Estate from iVillage
RealTalk @ Internet Crusade
REI Depot forums
Russ Whitney's Real Estate Investing Discussion Board
SDCIA Message Board - San Diego Creative Investors Association
The Neodemesne Discussion forum
The Real Estate Forums
Total Real Estate
U.S. Land Company

Articles of Interest

Informative articles on Real Estate Topics by Chet Boddy, Mendocino, CA
Adding Value to Real Estate by Chet Boddy, Mendocino, CA
The Seattle Times Home values

Continuing Education and more

Continuing Education Online
Dave Beson Life Success Seminars
isucceed.com
Julie Ryan - SuperStar System
KlockWorks - Joe Klock
Learning Pass
Mike Ferry Organization
Northwest Real Estate Institute
Quick Start Real Estate
Real Estate Academy - Washington State, California, Oregon & Nevada
Real Estate School
RealPro - Training and Consulting
Real Sure Group
Rockwell Institute
Star Power - Howard Brinton's outstanding training and coaching
The Real Estate School
Tom Hopkins - The Builder of Sales Champions

Periodicals (Paper and Web)

GlobeSt.com - Commercial Real Estate News and Property Resource
Journal of Property Investment and Finance
Multifamily Executive
National Real Estate Investor - commercial real estate investing and development
Real Estate Alert - The Weekly Update on Institutional Buying Opportunities
Real Estate Channel - BankRate.com
Real Estate Forum
Real Estate Marketing - Morningstar Multimedia
Realtor Today
Realty Times - Agent News and Advice

Recruiters

FPL Advisory Group - Corporate and Managerial Services
Whitney Group

Technology

Active Agent - Outlook-based Contact Management for the real estate agent
HP Real Estate Marketing Assistant
Investment Software
MLXchange - Web-based MLS system from Interealty
Mobile Listing Advantage - Access MLS data on your Blackberry
OpenMLS - The world's online multiple listing service
ProQuest - Touted as the THE BEST toll free provider
RealtyBid - Online Real Estate Auctions
Software Directory - Very complete list from the Texas Real Estate Institute

Buyer Oriented Sites

About.com - Home Buying and Selling Advice
Domania - Check recent home sale prices
HomeGain
HouseHunt
Real Estate ABC's - ABC's of real estate consumer guide
14 Mortgage calculators at RealEstateABC.com
Top 100 Real Estate sites at RealEstateABC.com
Real Estate Journal - Home Improvement
REALTOR.com Real estate listings & homes for sale
SellMyHome101

Unsorted

Arello's list of organizations
Arello's list of 'other links'
Castle Coalition - Citizens fighting Eminent Domain abuse
Calculators - Over 100 Personal Finance Calculators
EIFS and Building Defects
EIFS Alliance
EIFS Legal Network
Farm and Ranch Magazine Real Estate Listings - The Best of the Best
Home Ownership Advocates of Washington
IREM Home
LandVoice FSBO database
Manufactured Homes
NAREB.com
National Association of Real Estate Investment Managers (NAREIM)
NCREIF - National Council of Real Estate Investment Fiduciaries
NMHC - National Multi Housing Council
NWMLS
Pension Real Estate Association [PREA] - PREA Home
ProspecstPlus - Real Estate Agent Marketing
Real Estate Calculator Suite - Calculate financial scenarios to purchase/sell real estate
Real Estate Careers - Interviewing for a Position
Real Estate Relocation Coalition
Real Estate Research Institute
real estate transactions - an overview
REVA Network - Real Estate Virtual Assistant Network
real property (land law) - an overview
Realtor.org
RealTrends
Revised Code of Washington
Smartmoney.com Real Estate Home
Urban Land Institute
Washington Association of REALTORS®

Humor