Mathematical Reference 
Wolfram MathWorld 
a good online encyclopedia of mathematics 
Open Problems 
Open Problems
Project 
a list of open problems in computational geometry edited by
Demaine, Mitchell, and O'Rourke, including graph drawing problems. 
Conference 
Symposium on Graph Drawing
(2012,
proceedings)
(2013,
proceedings)
(2014
proceedings)
(2015
proceedings)
(2016)

An excellent source of current research in graph drawing. 
Munzner's InfoVis Resources 
InfoVis
Resources 
A list maintained by Tamara Munzner at UBC 
Munzner's upcoming InfoVis textbook 
Visualization
Design and Analysis: Abstractions, Principles, and Methods 

Conference 
Canadian Conference
on Computational Geometry 
Recent papers that have appeared at the conference are available
online. These sometimes include graph drawing problems. 
Conference 
Symposium
on Computational Geometry 
Recent papers that have appeared at the conference are available
online. These sometimes include graph drawing problems. 
Conference 
European Workshop
on Computational Geometry 
Recent papers that have appeared at the workshop are available
online. These sometimes include graph drawing problems. 
Conference 
Fall
Workshop on Computational Geometry 
Recent abstracts that have appeared at the workshop are available
online. These sometimes include graph drawing problems. 
Programming 
Computational Geometry Algorithms
Library (CGAL) 
library of algorithms implemented in C++ 