Sites

Physics Formulae (Popularity: )
http://www.xs4all.nl/~johanw/contents.html
A collection of frequently used physics equations compiled into several downloadable formats.

Eqndb (Popularity: )
http://www.eqndb.com
Search for physics equations and constants by keywords and symbols.

The Physics Reference (Popularity: )
http://dph1701.tripod.com/physsci/
Site contains every formula a first-year physics student is likely to run into.

The NIST Reference on Constants, Units and Uncertainty (Popularity: )
http://physics.nist.gov/cuu/Constants/
Values recommended for international use by the Committee on Data for Science and Technology, International Council of Science. Navigation is by text search.

The Laws List (Popularity: )
http://www.alcyone.com/max/physics/laws/
An alphabetical glossary of the various laws and theorems in this science.

Physical Reference Data (Popularity: )
http://physics.nist.gov/PhysRefData/
Held at NIST Physics Laboratory.

Physics FAQ (Where to Find It) (Popularity: )
http://www.faqs.org/faqs/physics-faq/where-to-find-it/
Links where to find the FAQ documents for physics.