eTV Prototyping Group
Georgia Tech’s eTV Protoyping Group.

International Academy of Web Television
Also gives out The Streamy Awards™.

AEDETI
Spain's Association of Interactive Television Companies.

AFDESI
The Association for the Development of Enhanced TV Services and Interactivity.

ATV Forum

Broadband Bananas

CableLabs®
Cable Television Laboratories, Inc. - Research and development consortium of cable TV companies for North and South America with initiatives for cable modems and digital cable TV.

EuroITV

IMPALA
MHEG-5 Interactive TV Middleware Advocacy Group.

Interactive Television Alliance

Interactive Television Committee
Click on "Interactive Television Committee" on the links.

Interactive TV Research - UITV.Info

InteractiveTV Today [itvt]

Java TV Developer's site

Linux4.TV

Linuxtv.org

OEDN.net

SAMBA
System for Advanced interactive digital television and Mobile services in BrAzil.

SUIT Project

The Advanced Television Enhancement Forum (ATVEF)
Former iTV industrial alliance.

The ELU TV project

TV Without Borders

TV-Anytime Forum

Academy of Television Arts & Sciences (ATAS)

Advanced Media Committee of the National Television Academy (The)

Advanced-television.com's huge List

AFI Digital Content Lab

AIMIA - Australian Interactive Media Industry Association

American Film Institute Digital Content Lab (The)
The Digital Content Lab was originally founded as the Enhanced TV Workshop to explore the possibilities of interactive television. (Formerly known as The Enhanced TV Workshop.) (At least temporarily closed in March 2010.)

Another list from this site
Dozens of listings.

Association for Maximum Service Television

Association of Radio Industries and Businesses of Japan

ASTRA Industry Excellence Awards - Best Interactive Television
The Australian Subscription Television and Radio Association (ASTRA).

BIMA Awards

British Columbia Technology Industry Association (BCTIA)

British Interactive Media Association

Cable Advertising Bureau

Cable Europe Labs

CableNET

Canadian Association of Broadcasters (CAB)

Canadian Film & Television Production Association
The CFTPA is a non-profit trade association representing almost 400 Canadian production companies involved in television, film and interactive media.

Canadian Interactive Alliance / Alliance interactive canadienne (CIAIC)

Canitec
Represents telecommunication networks in Mexico.

CASBAA
The Cable & Satellite Broadcasting Association of Asia.

Confederation of Aerial Industries (CAI)
UK

Connected TV Game Forum

Convergence: The International Journal of Research into New Media Technologies

CSELT & Telecom Italia Lab

CTAM
The Cable and Telecommunications Association for Marketing.

Deutsche Telekom Interactive TV Award
Type "interactive TV award" in search.

DigiTAG

Digital Display Working Group

Digital Europe

Digital Living Consortium

DIGITALEUROPE

DLNA

EIA (Electronic Industries Association)
Electronic groups, corporations and other entities that work together to have specified data transmission standards.

Electronic Frontier Foundation (EFF) (The)
Electronic Frontier Foundation is a nonprofit group working to protect your digital rights.

Electronics & Telecommunications Reseach Institute (ETRI)
Korea.

European Audiovisual Observatory

European Cable Communications Association

European Telecommunications Standards Institute

FiTV
Future interactive Television Project.

HbbTV Consortium

IAL Digital Entertainment Initiative

IMRG - (Interactive Media in Retail Group)

IMS Forum
IP Convergence.

Informa UK - (Digital TV Europe.net)
Interactive TV, TV/Internet convergence, broadband & more. Primarily for the European market. Type "interactive TV" in search.

Interactive Advertising Bureau (IAB)

Interactive Media Peer Group
The Interactive Media Peer Group was created by the Television Academy in 2000 and is responsible for the Interactive Media Emmys.

Interactive Ontario

International Television Expert Group

International TV Explorer

Internet Advertising Bureau UK

ITVStandards.org

Journal of Interactive Advertising
An Official Online Publication of the American Academy of Advertising.

LinuxTV Project

Maximum Service Television

Media Experiences 2 Go
Media Experiences 2 Go is an official blog out of the Motorola Home and Networks Mobility business.

MIPTV
Connection to the global entertainment content industry.

MIT Media Laboratory

Multichannel News
Type "interactive+TV" and "interactive+television" in search.

Multimedia over Coax Alliance (MoCA )

National Cable & Telecommunications Association
The National Cable and Telecommunications Association, formerly the National Cable Television Association, is the principal trade association of the cable television industry in the United States.

NATPE
National Association of Television Program Executives.

NBC Universal Technology Growth Center (TGC)

Ofcom

Open IPTV Forum

Open Screen Project
Led by Adobe and backed by others.

Project Canvas
Project Canvas - a joint venture to develop and promote a broadband enabled television platform.

T h i n k b o x
Thinkbox is UK television's marketing body.

Technology Association of America (The)

Television Bureau of Advertising

The Digital TV Group (DTG)
UK

The International Academy of Television Arts & Sciences
Now offering the Emmy for Outstanding Achievement in Interactive Television.

TV Interactiva
Espanol.

World Teleport Association