Dictionary.com- As far as online dictionaries are concerned, this one is pretty good. It also has a thesaurus function.
Biblomania.com- One of the most expansive online libraries I have found. Give it a look, you might find something interesting.
Bartleby Quotations Page- If you're looking for a famous quote to support your argument, or if you just want to impress me with sagacious words of wisdom, you may wish to start here.