The Internet Glossary of Statistical Terms
Glossary of terms organized according to learning order for those unfamiliar with the subject, and also an alphabetical list for already familiar with statistical procedure.

The Computational Beauty of Nature
Concise definitions, cross referenced, for the areas of computation that examine complex systems, fractals, chaos and adaptation.

Mathematical Thesaurus
Definitions of common mathematical terms, along with broader, narrower, and related concepts.