Instruments
Ambry - Batteries and other spare parts for Compaq Pocket PC's
Becker Avionic Systems
Blue Sky Avionics - Ball Varios and other instruments
Bohli 
Borgelt Instruments
Cambridge Aero Instruments
Cair Aviation Ltd - a UK producer of variometers, and general instrument supplier
CEGlide - Affordable final glide software for soaring pilots
Composite Technologies - Gauteng, South Africa
Crabb Computing - UK retailer of soaring software and instruments
Craggy Aero
Cumulus Soaring, Inc. - Paul Remde - Instruments, software and accessories.  Cambridge Aero Instruments, ILEC, LX Navigation, Filser, Tasman, Themi, Winter, Walter Dittel, Glide Navigator II, StrePla, SeeYou, flyWithCE, Flight Analysis, VL to IGC and EW to IGC, Goddard, GPS units from EMTAC, Rikaline, Transplant, RAM, Intercomp
Dittel, Walter - Radios
Eastern Sailplane
Electronic Thermal Detection - Martin Gregorie - Ground based solution for detecting thermals
Electronic Variometer - Marko Rocznik - Design of an electronic vario
Entec Technical Services - Horseheads, NY, USA, Dealer for Komet and Volkslogger
EW Avionics
Filser Electronic GmbH
Finesse Max - French retailer for Schleicher Sailplanes, instruments, software
Flight_Recorder_Filename_Decoder_V1.xls - by John DeRosa - Excel file that decodes IGC flight log filenames.
Garmin
Garrecht - Volkslogger
GPS Data Logger
Holtronic GmbH - Cenfis
How to Build Instruments for Hang Gliders - Fred Vachss - Interesting
ILEC GmbH
Knauff & Grove Soaring Supplies
LX Navigation
LX avionics Ltd - UK distributor for Filser and LX products, Oxfordshire, England
Mallettek Mini Vario
Ian McKee Aviation - Instruments, radios & maker of microphones and wingstands - NSW, Australia 
Microair Electronics Pty. Ltd.
Mountain High Equipment & Supply Co. - Aircraft Oxygen Equipment
New Technologies - Easy Matchbox Variometer - Italy
Nielsen Kellerman - NK Soaring Instruments
NMEA Recorder - Nick Bonničre
Peschges
PZL - WARSZAWA II S.A., Wytwórnia Sprzętu Komunikacyjnego (WSA) - Variometers, Airspeed Indicators, Altimeters - Poland
RD Aviation - UK - Online store is here
Sage Variometers
SDI Variometer - Varios, flight recorders, navigation
Soaring Books and Supplies - Bob Wander
SoaringPilot - Final Glide Calculator for Palm OS Devices - Free
Solaire Canada - Canadian Dealer for LS (Rolladen-Schneider) Sailplanes, instruments, trailers, etc.
Tasman Instruments - Instruments for Sport Aviation - Australia
Themi - Thermal Centering Device and Logger
Tiger Aviation Services - Online Aviation Superstore
Volkslogger
vPos - Virtual Position software and hardware for real-time tracking of gliders and viewing in 3D.
Westerboer
Wings & Wheels
WinPilot
Winter Instruments
Wytwórnia Sprzętu Komunikacyjnego (WSA), "PZL - WARSZAWA II" S.A.  - Variometers, Airspeed Indicators, Altimeters - Poland
XCOM Avionics - Aircraft radios and intercoms - Australia - Available from www.cumulus-soaring.com
Zander
Zaon Flight Systems, Inc. - Portable Aircraft Collision Avoidance Systems, Frisco, Texas, USA