General Curricula Vendors:

Robinson Curriculum --good as a resource for excellent books, if you don't mind printing them yourself.
Latter-day Family Resources --Good prices and low shipping charges on a large variety of books and subjects, plus some good book reviews and advice.
Greenleaf Press
Beautiful Feet Books

General Study Resources:

Study Web

General Worksheets:

Educast
RHL School
Worksheets Unlimited
Lesson Plans & Reproducibles at Scholastic
WorksheetFactory.com
Free Worksheets Website

Math Curricula Vendors:

Saxon Publishers
Key Curriculum Press
Latter-day Family Resources --Good prices on Saxon

Math Worksheets:

INEW Home Page
Educast --Has many math worksheets
RHL School --Has many math worksheets
SuperKids --Math Worksheet Creator

Math Skills Practice:

Education 4 Kids
Funbrain.com --Try Changemaker , Math Baseball , and others in their Numbers section
A+ Math
The ArithmAttack --You can download this onto your computer, and let you children time themselves while practicing math facts.

Math Online Resources:

Mathematically Correct

Books for Teaching Reading:

Teach Your Child to Read in 100 Easy Lessons
Bob Books

Phonics Help:

TampaReads.com --Reading Support Activities and Worksheets for K, 1st, 2nd, 3rd and 4th

E-Text Books & Poetry:

Project Gutenburg
221B Baker Street --A collection of 48 of Sir Arthur Conan Doyle's Sherlock Holmes books
The Complete Works of William Shakespeare --Comedy, History, Tragedy & Poetry
AESOP'S FABLES --Fairy Tales of Hans Christian Andersen
Works by Plutarch --Part of the Internet Classics Archive
Acacia Vignettes Stories
The Poetry Archives eMule.com
Sonnet Central --archive of English sonnets, commentary, pictures, and relevant web links

Reading Lists:

The 1000 Good Books List
Lynn's Very Un-Official Charlotte Mason Type Booklist
Education Reporter --The Ultimate Reading List--Classics That Endure
Education Reporter --A Child's Reading List
Newbery Medal Home Page
Caldecott Medal Home Page
Greenleaf Press --Their catalog makes a good reading list.
Beautiful Feet Books --Their catalog makes a good reading list.

Reading Incentives:

Book Adventure --Sylvan Learning Foundation

Handwriting:

Modern Italic Handwriting
'The Good Handwriting Initiative'
12 Rules for Good Cursive Handwriting
Handwriting Page Maker
Worksheets Unlimited --Has many handwriting worksheets

Books for Teaching Grammar:

Simply Grammar
Write Source 2000

Grammar Online Resources:

Elements of Style

Grammar Worksheets:

RHL School --Has many grammar worksheets

Grammar Fun:

Wacky Web Tales --Like Mad Libs

Copywork Help:

Copywork Online Resources:

Daily Dose of Dickens
Quoteland

Writing Help:

Outta Ray's Head--Writing Lessons
Writing a Basic Essay
CCI's Writing Process for Research or Literary Essays

Spelling Help:

Charlotte Mason said, "the gift of spelling depends upon the power the eye possesses to "take" (in a photographic sense) a detailed picture of a word; and this is a power and habit which must be cultivated in children from the first."

She also said, "Every misspelt word is an image in the child's brain not to be obliterated by the right spelling. It becomes, therefore, the teacher's business to prevent false spelling, and, if an error has been made, to hide it away, as it were, so that the impression may not become fixed."

TampaReads.com --Reading Support Activities and Worksheets for K, 1st, 2nd, 3rd and 4th

History:

The History Channel Classroom Calendar
AandE.com Classroom Calendar
Greenleaf Press --You can use their catalog as a resource for studying history chronologically.

Book of Centuries and Timeline Resources:

Our Timelines on Linda's Homeschool Page
Peg's History Notebook on Peg's Helpful Homeschooling Website

American History:

American Heritage Library
History for Homeschoolers
INS Naturalization Self-Test

Geography:

National Geographic Xpeditions

General Science Links:

Odyssey Magazine
Nye Labs Online
Virtual FlyLab
Discover Magazine
The Mad Scientist Network

Creation Science Links

The Great Dinosaur Mystery
LDS Creation
The Institute for Christian Research

Books on Nature Notebooks:

Wild Days: Creating Discovery Journals
Handbook of Nature Study

Nature Notebook Online Resources:

Nature Notebooks --Part of Penny Gardner's Charlotte Mason Approach to Education
Wild Days

Nature Study Online Resources:

Butterflies of North America