Open Problems

The Boise Problem Book
Problems in combinatorial set theory and topology, collected by Marion Scheepers.
http://math.boisestate.edu/~marion/research/BoiseProblemBook/

Kirby's Problem List in Low-Dimensional Topology
Problems list in PostScript format.
http://www.math.berkeley.edu/~kirby/

Open Problems in Topology
Collection includes problems in set theory, continua, algabraic structures, analysis, and dynamics. Page includes glossary of terms. Links are in PDF.
http://www1.elsevier.com/homepage/sac/opit/toc.htm

Thrackle.org
John Conway's Thrackle Conjecture: a compilation of what is known about the question.
http://www.thrackle.org/