LINGUIST List [Subscribe to get the latest information about all things linguistics!]
OED Newsletter (Oxford Languages Newsletter)
OED Word of the Day [see this blog entry too]
Old English Newsletter (OEN) ['a source for news, announcements, and information about the study of the culture and history of England between the years 550 to 1066'; open access!]
ADS-L ['a discussion list for members of the American Dialect Society and interested non-members ... Our primary topic of conversation is dialects of North American English, but we do wander off topic frequently.']