This sites lists some of the organizations that are in some way related to the teaching and learning of German (as well as other languages). 

ACTFL American Council for the Teaching
of Foreign Languages
CAL Center for Applied Linguistics
IDS Institut für deutsche Sprache 
GLSC German Language School Conference
Goethe Institut Goethe Institut in New York City
GI Trainernetzwerke Trainernetzwerke der Goethe Institute in den USA
IDV Internationaler Deutschlehrer Verband
MLA Modern Language Association
NECTFL Northeast Conference of Teachers of 
Foreign Languages
NYSAFLT New York State Association of Foreign
Language Teachers