Mastering English language

Strunk, William, Jr. 1918. The Elements of Style Asserting that one must first know the rules to break them, this classic reference book is a must-have for any student and conscientious writer. Intended for use in which the practice of composition is combined with the study of literature, it gives in brief space the principal requirements of plain English style and concentrates attention on the rules of usage and principles of composition most commonly violated.

Common Errors in English http://www.wsu.edu:8080/~brians/errors/errors.html

Guide to Grammar and Writing (including online tests)
http://grammar.ccc.commnet.edu/grammar/

Improve your English by the Hindu http://www.hinduonnet.com/thehindu/edu/arcedu.htm

English Usage, Style & Composition (American Heritage® Book of English Usage. ) http://www.bartleby.com/usage/

English sayings and customs http://www.rootsweb.com/~genepool/sayings.htm