ISGCI is an encyclopaedia of graph classes with an accompanying java application that helps you to research what’s known about particular graph classes. You can:

check the relation between graph classes and get a witness for the result
draw clear inclusion diagrams
colour these diagrams according to the complexity of selected problems
find the P/NP boundary for a problem
save your diagrams as Postscript, GraphML or SVG files
find references on classes, inclusions and algorithms