East Side, West Side Lecture notes by Herbert S. Wilf on generating combinatorial objects and Maple. http://www.cis.upenn.edu/~wilf/lecnotes.html
The Cutting Sticks Problem An unsolved combinatorial problem by Frans Faase. http://home.wxs.nl/~faase009/cutsticks.html
CADCOM Committee for the Advancement of Discrete and Combinatorial Mathematics. http://www.dms.auburn.edu/~rodgec1/cadcom/
Generating Functions Introduction to generating functions with interactive java applets by Alexander Bogomolny. http://www.cut-the-knot.org/blue/GeneratingFunctions.shtml
Operational Research Programming Trivia Computer code for research algorithms in operational research and combinatorial optimization. http://www.ortrivia.com/
British Combinatorial Committee Conference listings, bulletin and links maintained by Peter Cameron. http://www.maths.qmw.ac.uk/~pjc/bcc/
The Combinatorial Object Server Select a type together with specific parameter values and COS will return a list of all such combinatorial objects. http://www.theory.csc.uvic.ca/~cos/
Combinatorial Catalogues Combinatorial objects such as graphs, designs and geometries collected by Gordon Royle. http://www.cs.uwa.edu.au/~gordon/data.html
CATS: Combinatorial Algorithms Test Sets Searchable index of problems, links and methodology maintained by the Association for Computing Machinery. http://www.jea.acm.org/CATS/
Amazing Mathematical Object Factory Generators for several basic combinatorial objects by Frank Ruskey and Scott Lausch. http://www.schoolnet.ca/vp-pv/amof/
A Survey of Venn Diagrams Various facts and figures about Venn diagrams by Frank Ruskey. http://www.combinatorics.org/Surveys/ds5/VennEJC.html
G-Systems Theory of chord structures to create music through algorithms by Vladimir Ladma. http://www.sweb.cz/vladimir_ladma/english/music/articles/dide99.htm
Combinatorics Subfields in the AMS MSC 2000 classification 05. http://www.ams.org/msc/05-xx.html
Combinatorial Data Brendan McKay's collection of miscellaneous tables in graph6 or sparse6 format. http://cs.anu.edu.au/~bdm/data/
The Hyperbook of Combinatorics A project to develop a hypertext on major topics in combinatorics. http://www.combinatorics.net/hyper/
Catalogue of Lattices A catalogue of different types with applications to packing spheres by Neil Sloane and Gabriele Nebe. http://www.research.att.com/~njas/lattices/