ACLU: From its inception, the United States has been a multilingual nation.
A briefing paper (FAQ) from the ACLU on the history of language legislation.

Bilingual Resources
Resources about living with multiple languages.

The Debate Over English Only
Resources from the National Education Association. Includes a brief history of language inclusion.

English First
Official site for a group fighting to make English the official language for the country. Has several speeches, news articles and links.

¿English Only?
A collection of articles showing both sides of the argument. They are for multilingualism. [English/Español]

English Language Advocates
Appears to see the English language as being oppressed, and refers to other languages as "rivals". Includes current news about the debate.

Language Policy Web Site & Emporium
A collection of articles and resources from a James Crawford who focuses on the politics of language and is an advocate for language rights.

Language Rights and New Mexico Statehood
An examination of the rights of Spanish speakers as they entered statehood.

National Council for Languages and International Studies (NCLIS)
Promoting "international education" as a means of survival for the nation.

US English
Official site for two sister organizations fighting to make the English language official. This is probably the most prolific organization, headed by two immigrants.