Open Problems

Combinatorics Problems
Combinatorics problems selected from math olympiads.
http://www.geocities.com/CollegePark/Lounge/5284/math/combinatorics.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/

Open Problems in Combinatorics
Features links to newsletters, workshops, and papers.
http://www.combinatorics.net/problems/

Past Open Problems
From the SIAM Activity Group Newsletter in Discrete Mathematics. In PostScript. Compiled by Douglas B. West.
http://www.math.uiuc.edu/~west/pcol/pcolink.html

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