Josh Cooper's Math Pages : Open Combinatorics Problems Offers descriptions of discrepancy, Euclidean Ramsey Theory, geometric graphs and hypergraphs. http://math.nyu.edu/%7ecooper/combprob.html
Open Problems for Undergraduates A collection of open problems in Discrete Mathematics which are currently being researched by members of the DIMACS community. http://dimacs.rutgers.edu/~hochberg/undopen/
Problems in Graph Theory and Combinatorics A collection maintained by Douglas B. West, of the University of Illinois. Features brief introductions, along with references cited. Topics include matching and independence, connectivity, graph homomorphism and circular coloring. http://www.math.uiuc.edu/~west/openp/
Some Problems in Matroid Theory Thomas Zaslavsky of Binghamton State University of New York presents brief descriptions and references. Find information on Bonin's Projective Bound including the maximum r-flat, covering and packing by flats. http://www.math.binghamton.edu/zaslav/Matroids/matroidprobs.html
Help build the largest human-edited directory on the web.