General English Links:

http://dictionary.cambridge.org/

Cambridge Dictionaries online

http://powerreporting.com/

Power Reporting for Journalists- "Here are thousands of free research resources for journalists, annotated and updated daily: Find people and companies; Check facts; Find data for your beat; Try new search tools; Subscribe to news alerts; Plan newsroom training."

Literature:

http://www.xs4all.nl/~pwessel/writers.html

Great Writers- poets and writers from ancient to modern times. Biographical information on many of the names covered. 

http://andromeda.rutgers.edu/~jlynch/Lit/

English and American Literary Resources- page by Prof. Jack Lynch, University of Pennsylvania-- has some broken links. 

Grammar:

http://www.edufind.com/english/grammar/

Online English Grammar- information on the proper use of the parts of speech, from the Digital Education Network Ltd. 

http://www.southwestern.edu/%7Ecarlg/Latin%5FWeb/glossary.html

Chart of Grammatical Terms- a chart of grammatical terms.

Poetry:

http://www.bartleby.com/verse/

Both American and British-

"This poetry site (at Bartleby.Com) contains five separate collections of poetry: 1)The Oxford Book of English Verse; 2) Yale Book of American Verse; 3) Modern British Poetry; Modern American Poetry; 4) Metaphysical Lyrics & Poems of the 17th C.; and 5) The Golden Treasury. The collections may be searched by keyword, and browsed via: Indexes to Poems: Chronological, Author, Title, First Line"