TwinStuff.com
Bulletin boards, twin games, photo gallery, information for parents, TV and movie twins, twin events, and information.

The Center for Study of Multiple Birth
A resource for research and information about the causes, effects and problems of multifetal pregnancy.

Facts About Multiples
Information on twins, triplets, quadruplets, quints and higher order multiples. Features a database of multiple birth families, statistics, basic information on twinning and a message board.

TwinMajority.org
From 2127, most babies will be twins. This site explains why evolution predicts this.

Twinsworld
Offerings include a twin casting agency, twin events, reunion of twins placed for adoption or separated at birth, message boards, links, photos, contests, and research.

The International Twins Association
A non-profit, family-oriented organization to promote the spiritual, intellectual, and social welfare of twins and multiples throughout the world.

Twins by Twins
This site is built for all those that want to learn more about twins and is dedicated to those that are twins and proud of it.

Twins Network
A resource for understanding twins and sharing information. Surveys, facts, news, trivia, links.

Mid Atlantic Parents Of Multiples
A State Association that brings together Mothers of Multiples Clubs. Birth statistics, conventions, members section, photo gallery.