A list of glossaries put together by Larry Ferlazzo in 2009, including
A (Mostly) Complete Glossary for ESL EFL Teaching From Heads Up English
ESL Glossary From Bogglesworld
ESL Terminology From State University of New York — Courtland
ELT Terminology, Abbreviations & Acronyms From TEFL.net
Understanding Second Language Terminology From Everything ESL
The British Council’s Teaching Knowledge Database
Teaching Foreign Languages Glossary from Annenberg
Via Shona Whyte