english language spelling rules

An excellent guide to english spelling rules can be found at the davidappleyard.com World of English Hub.

The other resources on the site include:

English User's Bookshelf
Dictionary Bank
Grammar Glossary
Article Usage
Tense Usage
Irregular Verb Chart
Irregular Verb Patterns
Pronunciation
Punctuation
Spelling
Territory-Related Words
Words Often Confused
American-British Glossary
British-American Glossary
Phonesthemic Initials