New York: Modern Language Association, 1921–. See this entry in Databases and Indexes in Literature, page 40.
http://www.ethnologue.com. A database of information on world languages, including information about geographic distribution, dialects, numbers of speakers, and linguistic affiliation. The site includes a bibliography. Maintained by SIL International, an organization that promotes language study for international faith-based work, this database is particularly strong for basic information about lesser-known and endangered languages.
http://www.ilovelanguages.com. Formerly known as The Human-Languages Page, this site offers links to language-related Internet resources. Of particular interest is the Languages section, which contains categories such as languages, dictionaries, lessons, and so on.
Ed. Nancy H. Hornberger. 2nd ed. 10 vols. New York: Springer, 2008. Covers a wide range of topics, from bilingual education and language policy to language testing and research methods.
Ed. William J. Frawley. 2nd ed. 4 vols. New York: Oxford University Press, 2003. Includes scholarly articles on all aspects of linguistics along with helpful bibliographies for further research.