- Decomposition matrix archive of blocks of simple groups, kept at RWTH Aachen by Thomas Breuer, with information extracted from the GAP library.
- Malka Schaps' block database contains data on blocks of alternating, symmetric and sporadic groups, as well as lists of blocks with cyclic defect groups.
- The Groupprops site uses the SmallGroup labellng and gives detailed information on each group. We use this for labelling defect groups.
- nLab is a wiki site concerning category theory, especially higher categories. The viewpoint is more from physics and the material is more abstract than that presented here.