There are a ton of great resources for designers, but I have
collected a list of just the resources that I am personally familiar with.  I will continue to add to this list.
E-Books (These two e-books make a great set because they teach different things.)
Forming Shawls and
Their Charts- Francoise Danoy (Aroha Knits)   Ravelry
ShawlStar: Your Comprehensive Guide to 43 Shawl Shapes-
Knotions Magazine    Affiliate link
Stitch Dictionaries
750 Knitting Stitches:
The Ultimate Knit Stitch Bible- Pavilion Books    Amazon
The Crochet Stitch
Bible- Betty Barnden    Amazon
Japanese Knitting
Stitch Bible- Hitomi Shida (translated by Gayle Roehm)    Amazon
Knitted
Embellishments: 350 Appliques, Borders, Cords, and More- Nicky Epstein    Amazon
Knitted Lace of
Estonia- Nancy Bush    Amazon
Knitting Brioche Lace-
Nancy Marchant    Amazon
Knitting Fresh Brioche: Creating Two-Color Twists and Turns-
Nancy Marchant    
The Magic of Shetland
Lace Knitting- Elizabeth Lovick    Amazon
Traditional Knitted
Lace Shawls- Martha Waterman    Amazon
Traditional Knitting
Patterns- James Norbury    Amazon
Designing Books
The Beginner’s Guide
to Writing Knitting Patterns- Kate Atherley    Amazon
Knitwear Design
Workshop: A Comprehensive Guide to Handknits- Shirley Paden    Amazon
Little Red in the City- Ysolda Teague Amazon
Little Red in the City- Ysolda Teague Amazon
Technique Books
Cast On, Bind Off: 211
Ways to Begin and End Your Knitting- Cap Sease    Amazon
The Essential Guide to
Color Knitting Techniques- Margaret Radcliffe    Amazon
Folk Shawls: 25
Knitting Patterns and Tales from Around the World- Cheryl Oberle    Amazon
Increase Decrease: 99
Step-By-Step Methods- Judith Durant    Amazon
Knitting Around the
World- Lela Nargi    Amazon
Knitting Vintage Socks-
Nancy Bush    Amazon
The Knowledgeable
Knitter- Margaret Radcliffe    Amazon
The Principles of
Knitting- June Hemmons Hiatt    Amazon
Vogue Knitting: The
Ultimate Knitting Book- the editors of Vogue Knitting Magazine    Amazon
Sizing Charts
Child Sizes Chart
Children's Size Charts
Standard Body Measurements- CYC
Multisize Me- Knitty
Sizing Chart- Ysolda Teague
Magazines
Vogue Knitting
Courses
Blogs
Podcasts