- Combinatorial Problems I Like, by Josh Cooper
- Open Problems - Graph Theory and Combinatorics, by Douglas B. West
- Open problems in combinatorics (pdf file) , by Alexander Postnikov
- Positivity Problems and Conjectures in Algebraic Combinatorics, by Richard Stanley
- Ten Problems in Combinatorics, Lecture given by Gian-Carlo Rota at the Conference on Combinatorics and Physics (CAP'98), held at the Los Alamos National Laboratory, August 10-12, 1998. To be announced.
- Open Problems from the SIAM Activity Group Newsletter in Discrete Mathematics
- Problems on the Enumeration of Matchings (ps file) , by James Propp
- Unsolved Combinatorial Problems, by Zsolt Tuza
- Open Problems on Perfect Graphs, by Vašek Chvátal
- Problems in Signed, Gain, and Biased Graphs, compiled by Thomas Zaslavsky
- Unsolved Problems in Graph Theory, compiled by Stephen C. Locke
- Open Problems of Paul Erdös, by Fan R. K. Chung
- A list of problems on permutation groups, by Peter J. Cameron
- A problem on transitive permutation groups, by Peter J. Cameron
- Some Problems in Matroid Theory, compiled by Thomas Zaslavsky
- Unsolved Mathematics Problems, compiled by Steven Finch.