e-Reference

A computational knowledge engine: it generates output by doing computations from its own internal knowledge base, instead of searching the web and returning links. Continually updated. A free online resource.

ChemSpider is a free chemical structure database providing fast access to over 30 million structures, properties and associated information. By integrating and linking compounds from more than 470 data sources, ChemSpider enables researchers to discover the most comprehensive view of freely available chemical data from a single online search. It is owned by the Royal Society of Chemistry

A SpringerReference database comprising of hundreds of academic review articles from over 31 encyclopedias from 1968 to the present. You can search across all encyclopedias and find entries for individual terms, topics, and subjects. Remarkable and a first choice!

A comprehensive academic earth sciences wiki.

From the makers of Wolfram Alpha and Mathematica, MathWorld is the web's most extensive mathematical resource, provided as a free service to the world's mathematics and internet communities and covers Algebra, Applied Mathematics, Calculus and Analysis, Discrete Mathematics, Foundations of Mathematics, Geometry, History and Terminology, Number Theory, Probability and Statistics, Recreational Mathematics, Topology.

A first stop for any math or stat resource!

A first stop for quick references, citations and explanations.