Here's a list of well known mail order companies that specialize in hobby and aircraft supplies (in no particular order):

Here's a list of manufacturers/builders that create and/or distribute sailplanes and other aircraft:

• Aerofoam Radio Control - Mark Mech's Combat Sailplanes
• BASH Enterprises - Home of the Mongo combat sailplanes
• Combat Wings- The best place to get RTF Boomerangs
• Maple Leaf Design - The Ultimate in HLG, 2M and F3J Molded Sailplanes
• Multiplex USA - sailplanes, radios, and more...
• Dave's Aircraft Works - handlaunch, combat and other EPP foam durable sailplanes (Now SkyKing RC Products)
• DJ Aerotech - handlaunch and other sailplanes
• Dream-Flight - makers of Alula slope plane (and others)
• Enduro Composite Models - handlaunch sailplanes
• Goldberg Models - makers of various types of aircraft for many years
• Hobbies.Net - a division of Tower Hobbies with misc. hobby 'things'
• Hobby Club - planes, sailplanes, electric, motors, etc.
• Kyosho - planes, sailplanes, helicopters, etc.
• ICARE Sailplanes - Sailplanes, Electrics, Handlaunch planes
• MM Glider Tech - Slope, Combat, Handlaunch, and 2 meter R/C Sailplanes and free flight
• Northeast Sailplane Products - Every kind of sailplane and lots more
• Phoenix Model Products - Manufacturers of Slope Sailplanes
• Pibros "Foamie" Flying wing - the Famous Pibros Delta Wing
• R/C Direct - R/C airplanes and sailplanes
• RnR Products- R/C aircraft, high-performance sailplanes, UAV/RPV, and other research aircraft
• Sky Bench Aerotech - Lots of model aviation, including sailplanes
• SkyKing RC Products - Unique sailplanes and current manufacturer of Dave's Aircraft Works planes
• Top Flight - planes and covering materials
• Windrider Hong Kong - makers of unique electric and slope planes, including the new A388 Airliner slope plane
• Wowings - makers of EPP flying wings for Slope/Combat.
• Trick R/C - makers of Zagi slope combat planes

Here's a list of manufacturers, distributors, or related components like radios, servos, electric motors, tools, etc.:

• Ace Wing Carriers - Airplane and Helicopter wing and flight bags
• Airtronics Inc.- Airtronics Radio Systems
• AstroFlight Inc.- electric motors and controllers
• Cirrus Servos - Quality replacement servos for your planes
• Compu-FoamCore - Computer accurate cutting of your foam cores!
• Dremel electric tools - Hand Rotary Cutting tools and more
• Don Edberg's Books on Programming Computer Radios - Programming the Futaba Series 8 Radios and more
• Endless Lift (RadioCarbonArt)- soaring videos describing flying techniques and narratives
• FMA Direct- lightweight, high quality radio receivers and servo products
• Futaba- Futaba Radio Systems
• Global Hobby Distributors- list of retail outlets carrying Global Hobby products
• Hanley Innovations VisualFoil- airfoil plotting program
• Hitec- radio control systems and accessories
• Horizon Hobby- JR radio control systems and other products
• Plaid Sneaker Productions / BASH Combat Videos- California Combat video
• Panavise tools - Specialized Tools for the Hobbiest
• R/C Trainer- Transmitter to computer flight simulator interface
• ScrollSander- small parts sanders
• Sirius Electronics (Peak Electronics)- home of the Sirius Pro Series NiCad Charger
• Soaring Stuff- Soaring and construction videos and misc. parts for building sailplanes
• Tom's R/C Electronic Regulator Circuit
• Xenon Project - distributors of Electric planes and helicopters

Here's a list of links to other pages that have R/C Sailplane links (and other things, such as electronic projects!):

• Electric Hobby Projects [thanks AppliancePartsPros.com & Josh]
• R/C Web Directory
• Glue-It.com - Information about building all kinds of models, including shops, museums, and galleries
• GliderKing - Everything, absolutely everything to do with soaring (zillions of pictures)
• PicaSim - Flight Simulator for radio controlled aircraft - Great Sailplane Simulator with very simple controls.
• R/C Slope and Power - Personal site with reviews of older and newer kits and other info
• Michael Shellim's R/C Soaring page (UK based)
• The Torrey Pines Gulls
• South Bay Soaring Society
• PJ Model Classics - R/C scale plane plans
• SFS Soaring Simulator - German Scale-Flight simulator
• Soaring FAQ - Frequently asked questions about soaring