Nintendo has made a list of over 25 new developers that have signed on to develop for either the Gamecube or Game Boy Advance. Check 'm out!

-03 Games/Starbreeze Studios- GBA developer
-Adeline Software International-GBA developer
-Atod AB-GCN
-Babel Media-GCN and GBA
-CABOSoft LLC-"
-Codemasters-GCN
-Coyote Developments Ltd.-GCN
-Eden Studios-GCN
-Free Radical Design Ltd.-GBA
-Full Fat Productions Ltd.-GCN
-Handheld Games-GCN
-I Wish (Games) Ltd.-GBA
-M4 Ltd.-GCN
-Monster Games Inc.-GCN and GBA
-n-Space, Inc.-GCN
-N.A.P.S. Team S.N.C.-GCN and GBA
-Netdol Entertainment-GCN
-Outrage Entertainment, Inc.-GCN
-Puzzlekings LImited Liablity Partnership- GCN and GBA
-Runecraft,Ltd.-GCN
-Semi Logic Entertainments-GBA
-Snowblind Studios-GCN
-Studio 3 Interactive Entertainment-GCN
-Taniko-GBA
-Vivid Image Developemtn Ltd.-GBA
-Wahoo Studios-GCN

Source: Nintendo Power