Algebra

Robbins Algebras Are Boolean - A web text by William McCune describing the solution of this problem by a theorem-proving program, with input files and the proofs.
http://www.cs.unm.edu/~mccune/papers/robbins/

Abstract and Linear Algebra - A forum for students on abstract algebra and linear algebra.
http://www.math.miami.edu/forum/algebra/

Abstract Algebra - Lecture notes by David Wilkins, Trinity College, Dublin. Topics in Number Theory; Group Theory; Galois Theory.
http://www.maths.tcd.ie/~dwilkins/Courses/311/

Homogeneous Transformation Matrices - Explicit n-dimensional homogeneous matrices for projection, dilation, reflection, shear, strain, rotation and other familiar transformations.
http://www.silcom.com/~barnowl/HTransf.htm

A Catalogue of Lattices - By Gabriele Nebe and Neil Sloane.
http://www.research.att.com/~njas/lattices/

Intro to Abstract Algebra - Paul Garrett's detailed and comprehensive lecture notes in abstract algebra.
http://www.math.umn.edu/~garrett/m/intro_algebra/index.shtml

Math Forum: Algebra Problem of the Week - A weekly interactive project for algebra on the Internet. Challenging problems are posted and solutions appear on the Web.
http://mathforum.org/algpow/

Octonions and Sedenions - Enter the world of 8 and 16 dimensional hypercomplex numbers and discover that the laws that are taken for granted, but do not always hold true.
http://www.geocities.com/zerodivisor/

All About Circuits - Boolean Algebra - An introduction to boolean algebra from the perspective of electronic engineering.
http://www.allaboutcircuits.com/vol_4/chpt_7/index.html

An Introduction to the Algebraic Specification of Abstract Data Types - Jean Baillie, Department of Computer Science, University of Hertfordshire.
http://homepages.feis.herts.ac.uk/~comqejb/algspec/pr.html

Algebra Links - From Spartanburg County School District Two.
http://www.spartanburg2.k12.sc.us/links/algebra.htm

Algebraic Areas of Mathematics - Topics include number theory, groups and sets, commutative rings, algebraic geometry, and linear algebra.
http://www.math.niu.edu/~rusin/known-math/index/tour_alg.html

Defining Boolean Algebra - Defines and compares the postulates and use of symbols between Boolean and regular algebra.
http://jairosoft.com/j/intro_math13.htm

Lecture Notes in Algebra and Number Theory - Andrew Baker, University of Glasgow.
http://www.maths.gla.ac.uk/~ajb/course-notes.html

Univalg Mailing List - Mailing list for use by the Universal Algebra community. Universal Algebra is a technical branch of mathematics related to algebra and model theory.
http://groups.yahoo.com/group/univalg/

Harmonic Polynomials for the Symmetric Group and Macdonald Symmetric Polynomials - Offers outline of the problem, bibliography, and math tables. Resources assembled by François Bergeron.
http://bergeron.math.uqam.ca/conjecture_fact.html

VectorLand - An online course to get to grips with 3D vectors. Most of the material is about UK A-level difficulty.
http://members.tripod.com/~Paul_Kirby/vector/VectorLand.html

FDLIST - Information on representation theory of finite dimensional algebras. Papers, meetings, places, people, jobs, journals, software.
http://www.mathematik.uni-bielefeld.de/birep/fdlist.html

IDA: Algebra Interactive - An HTML-based book by Arjeh M. Cohen, Hans Cuypers and Hans Sterk. It focuses on an algorithmic approach to algebraic structures. Many of these tools and examples use the computer algebra package GAP. Site has samples and errata.
http://www.win.tue.nl/~ida/

What is a Jordan-like Algebra? - Includes generalizations, and algebraic geometry. Notes and links by Tony Smith.
http://www.valdostamuseum.org/hamsmith/Jordan.html

Abstract Algebra Online - Contains many of the definitions and theorems from the area of mathematics generally called abstract algebra. Intended for undergraduate students taking an abstract algebra class at the junior/senior level, as well as for students taking their first graduate algebra course.
http://www.math.niu.edu/~beachy/aaol/

Home Page of J. S. Milne - Includes preprints and course notes on Group Theory, Fields and Galois Theory, Algebraic Geometry, Algebraic Number Theory,Modular Functions and Modular Forms, Elliptic Curves, Abelian Varieties, Etale Cohomology, and Class Field Theory.
http://www.jmilne.org/math/

Dave's Short Course on Complex Numbers - An introduction with math and a little history intended for those having a familiarity with ordinary real numbers and algebra.
http://www.clarku.edu/~djoyce/complex/

Cohomology of Modules over the Mod 2 Steenrod Algebra - Robert R. Bruner, Wayne State University. Tables in PS or GIF formats.
http://www.math.wayne.edu/~rrb/cohom/

Center for Commutative Algebra - A site for the commutative algebra community, including news, conference and preprint announcements, and a huge list of algebraists.
http://www.commalg.org/