The New Laws of Gravity
Online book introducing a scalar theory of relativistic gravity, including applications to antigravity, cosmology, quantum gravity, and gravitational radiation; by Paul Bird.
http://users.whsmithnet.co.uk/paulbird/gravbook/

EDCON Gravity and Magnetics
Gravity and magnetic data acquisition, processing and interpretation. Specializing in airborne, borehole, land and marine gravity and magnetics for environmental, engineering and energy industries.
http://www.edcon.com/

Knelson Gravity Solutions
KGS, provides total gravity concentration solutions. A full range of products and services are available including gravity amenability testing, flow sheet development, circuit engineering and supply of turnkey gravity circuits worldwide.
http://www.knelsongravitysolutions.com

Matters of Gravity (2006-present)
Newsletter of the American Physical Society's Topical Group on Gravity, published two times a year, which gives a highly informative overview of recent developments in gravity and general relativity research. Site contains links to the editions Fall 2006 and later.
http://www.oakland.edu/physics/Gravity.htm

Gravity Flow Systems Southwest, Inc.
Manufacturers of gravity solids/liquid separation equipment, Wedgewater Filter Bed, Lateral Flow Thickener, Intake Screens, Wedgewater Sieves, Wedgewater DCF
http://www.gravityflow.com/

Matters of gravity (1991-2006)
Newsletter of the American Physical Society's Topical Group on Gravity, published two times a year, which gives a highly informative overview of recent developments in gravity and general relativity research. Site contains links to the editions Fall 1991 to Spring 2006.
http://www.phys.lsu.edu/mog/

Knot Theory and Quantum Gravity
Quantizing general relativity brings knot theory into quantum gravity. The Jones polynomial is shown to give rise to physical states of quantum gravity. Links to research papers by the author.
http://www.phys.lsu.edu/faculty/pullin

Gravity Recovery and Climate Experiment (GRACE)
GRACE will be able to map the Earth's gravity fields by making accurate measurements of the distance between two satellites, using GPS and a microwave ranging system. It will provide scientists with a way to map the Earth's gravity fields. The results from this mission will yield information about the distribution and flow of mass within the Earth and its oceans and surroundings.
http://www.csr.utexas.edu/grace/

An alternative theory of gravity
There is no 'gravitational force'. The universe is expanding, and 'gravity' is one of the results.
http://www.copples.clara.net/gravity.htm

Washington University Gravity Group
Washington University Physics Department Gravity Group
http://wugrav.wustl.edu/