http://rc-modeler.net/Balsakits.aspx: Links to a lot of kit manufacturers.
Aerosphere - Some classic Airtronics kits
Aeroworks Scale Aerobatics
Airflair Sport Planes
American Eagle Large Scale WW2 (Their site is no longer working)
Arizona Models Scale WW1
Aztec Air (Classic Pattern)
Bluejay (Bridi) (Vintage Pattern)
Bruce Tharpe Engineering (Balsa Sport Kits)
Carl Goldberg (Sport and Scale)
D&L Designs Sport Planes
Dynaflite (Sport and Scale)
Early Models (Classic and 1/2a)
Eureka (Classic Pattern)
Extream Flight RC Scale Aerobatics
Flair (UK) Scale and Sport
Gee Bee Kits - Contact Tower Hobbies
Great Planes (Sport and Scale)
Hobby Hangar (Scale and Sport)
Hobby Lobby (Sport and Trainer)
Home and Hobby Solutions (Classic Pattern)
House of Balsa (Small Scale and Sport)
Ikonwst (Giant Scale)
Iron Bay (Giant Scale)
Jack Stafford (Large Scale)
Juno RC Prop-Jets
Lanier A little bit of everything
Matney Models Racing planes (Q500)
Meister Scale WW2 Warbirds
Morris Hobbies (Profiles and Fun Fly)
Northeast Aerodynamics Sport Planes (Re-kit of the Pica Dualist)
Ohio Model Products (Flyin Things and Profiles)
Page Aviation (Gee Bee)
Proctor (Museum quality WW1 Scale)
Sig (Sport and Scale)
Select Hobbies 1/2a stuff
Skyshark RC (Warbird and Sport)
Sunset Models Scale (SR71, OV-10 Bronco etc)
Swaneys Hangar Profile and Fun-fly planes
Top Flite (Sport and Scale)
Top Notch Kits
VK (WW1 Scale)
Wing Manufacturer WW2 Warbirds
Yellow Aircraft Giant Scale WW2 and Jets