I've done some searching to find links relevant to issues and ideas mentioned in the Haggadah. They appear woven throughout the text of the online Haggadah. Where appropriate, the button links to the page of the Haggadah, otherwise the button links out. The number in brackets is the date [yymmdd] the item was added.
Much more exists than what I have here; I made an editorial decision about what I found interesting, unique, special and would serve as door-openers to further exploration.
This is a subject organized list of them. It exists as much for me to be able to check currently active links as it does for others to be able to use the Haggadah.
ORT's Pesach pages
Lights In Action Passover links
Learn about the holiday
Passover in Rome.
The Anonymous Haggadah
Chabad's Haggadah collection/bibliography
A Congregational Haggadah
Haggadah for the Liberated Lamb
The Howard Rheingold Family Haggadah
An Interactive Haggadah
The Parnes Haggadah
The Red Sea Haggadah
Temple Emanuel's Virtual Seder
Uncle Eli's Haggadah
The Zevach Pesach Haggadah
Rabbi Amy Scheinerman's Haggadah pages
The Sarajevo Haggadah
A Word of Art
Child-centered Passover Haggadot/stories of John Kador
Lights In Action four Questions
Four Questions of Meloncholy : Poems by Tomaz Salamun
Four Questions the Kidlink Response
Steve Gindi's interpretation
Lutheran guidelines for the use of the Passover Haggadah
Wine (see internally for multiple links)
A menu for the Seder meal
Bioethics and the Passover Lamb
Jewish Women jokes
Shoa' library online
Mahomet-Seymour Junior High School Holocaust Project
Mutual Aid and Self-Help Groups 
The Warsaw Ghetto Uprising
Terror in Israel
Congress of Secular Jewish Organizations
Jewish Agency For Israel
Jewish Reconstructionist Foundation
KTAV Publishing House
Mazon: A Jewish Response to Hunger
Temple Adat Shalom
Union of American Hebrew Congregations
Isidor Isaac Rabi
Apple Computers, Inc.
Apple Language Kits
Aridi Web Clips
Nisus Software Inc.
The City of Poway
"Judaism on the Web"
Last modified on 24 January, 2001