From the Early Days of the World Wide Web...

In the beginning, there was Donald Graft's Animal Rights Resource Site.  Before every animal group everywhere had their own website, ARRS was the one central websource for animal rights info.  After the cut are the essays from ARRS's Animal Rights Theory and Philosophy Section, courtesy of Archive.org's Wayback Machine:

Abortion versus Animal Rights by Ted Altar

The Alpha Centaurians Have Landed by Ted Altar

Animal Advocacy and Abortion by Larry Rosenfeld

Animal Rights and Animal Welfare by Gary L. Francione

Animal Rights and Animal Welfare: Five Frequently Asked Questions by Gary L. Francione

Animal Rights and Native Culture by Ted Altar

Animal Suffering by Donald Graft

Beyond Might Makes Right by Matthew Ball and Jack Norris

Claims of Rights are Often Wrong by Matthew M. Ball

The Core Idea, Problems, and Attraction of  Subjectivism by Ted Altar

The Diversionary Tactic of Plant Pain by Ted Altar

Do Animals Feel Pain? by Peter Singer

The Fallacies Behind the Plant Pain Argument by Ted Altar

Gaps in the Mind by Richard Dawkins

Ill-Gotten Gains by Tom Regan

Keeping Species on Ice by Mary Midgley

Moral Constraints and Animals by Robert Nozick

Peace on Earth by C. David Coates

Remember Socrates: Don't Eat Animals by John C. Champagne

The Rhetoric of Apology in Animal Rights by Dr. Karen Davis

The Scientific Basis for Assessing Suffering in Animals by Marian Stamp Dawkins

Secular Ethics and Animal Rights by Peter D. Wilson

The Vampire's Dilemma: Animal Rights and Parasitical Nature by Andrew Linzey

Xenografts and Animal Rights by Gary L. Francione