Grammar
Guide to Grammar and Writing - by Professor Charles Darling and Capital Community-Technical College
HyperGrammar - From The University of Ottawa
Grammar Handbook - University of Illinois at Urbana-Champaign
An Elementary Grammar - Looks great, but it's from an English site (The English Institute).
Literature
Project Gutenberg - On-line text of thousands of classic books. Great for electronic searching for details in a story if you can't quite remember where in the book a certain event took place or a character is introduced.
The On-Line Books Page - Thousands of on-line books.
Poets' Corner - Thousands of poems on-line (but none from my favorite, Ogden Nash :-( ).
Ogden Nash - To make up for the deficit at Poet's Corner :-) .
Book Units PreK-12th grade - Lessons and analysis of dozens of books.
Essay Writing
The UVic Writer's Guide - Wow - this is an incredible resource!
Reference
Encyclopedia Smithsonian: The Smithsonian from A to Z
Knowledge Adventure Encyclopedia
Infoplease Encyclopedia and Dictionary
FunkandWagnalls.com - Get Smart. Have Fun.
A
Web of On-line Dictionaries includes foreign languages