Links and subcategories within the Algebraic Topology section are provided below.
Directory Links:
Link: http://hopf.math.purdue.edu/pub/hopf.html

Encyclopedic reference for 'KTheory' in Dave Rusin's Mathematical Atlas. Includes a brief history along with various links to textbooks, reference works, and tutorials on the subject. Link: http://www.math.niu.edu/~rusin/knownmath/index/19XX.html

Handbook of algebraic topology Link: http://www.math.niu.edu/~rusin/knownmath/index/55XX.html

moscowpub.html Link: http://www.bangor.ac.uk/~mas010/intasrep.html

An encyclopedic reference containing definitions, some discussion, and an assortment of useful links to various resources concerning Algebraic Topology and KTheory. Link: http://en.wikipedia.org/wiki/Algebraic_topology

Index to more than 100 articles on Algebraic Topology. Link: http://mathworld.wolfram.com/topics/AlgebraicTopology.html

A downloadable textbook in algebraic topology Link: http://www.math.cornell.edu/~hatcher/AT/ATpage.html

Algorithms for the Fixed Point Property Link: http://www.csi.uottawa.ca/ordal/papers/schroder/FINSURVE.html

Includes information on subscribing, archives of past discussions, and links to home pages of algebraic topologists and other related resources. Link: http://www.lehigh.edu/dmd1/public/wwwdata/algtop.html

A downloadable textbook in algebraic topology Link: http://www.math.cornell.edu/~hatcher
