Mainstream Pattern Collections:
Burda
Butterick (owned by McCall's)
It's So Easy (owned by Simplicity)
KwikSew
McCall's
New Look (owned by Simplicity)
See & Sew (owned by McCall's)
Simplicity
Stitch N Save (owned by McCall's)
Vogue (owned by McCall's)
Specialized/Independent Pattern Collections:
Akasha
Amy Butler Sewing Patterns
The Batik Butik (also known as Bali Collection)
Christine Jonson Patterns (also known as CJ Patterns)
CNT Patterns
Collette Patterns
Cutting Line Designs
Donna Christopher Patterns (Could not find direct link, but available on major sites like sewingpatterns.com)
Dos de Tejas Patterns
Encore Design (Could not find direct link, but available on major sites like sewingpatterns.com)
Fig Tree & Co.
Folkwear
Ghees
Grainline Gear
Green Pepper
Heather Bailey Patterns
Hot Patterns
Indygo Junction
Islander
Jalie
Kayla Kennington
LaFred Patterns
Laura Marsh Designs
Lazy Girl Designs
LJ Designs
Loes Hinse
Lorraine Torrence (also known as Grainline Gear)
Lutterloh
Material Things
ModKid Sewing Patterns by Patty Young (Plus, Misses, Tweens and Children)
Neue Mode (also Young Collection, Quick & Easy)
Palmer Pletsch
Park Bench
Pat Bravo Patterns (Accessories Patterns)
Pavelka
Petite Plus
Portabellopixie Patterns
Purrfection
Rag Stock
Saf-T-Pockets
Sense & Sensibility
Serendipity Studio
Sewaholic (Specializing in patterns for the "Pear-Shaped" Lady)
Sewing Workshop
Tina Givens
Wild Ginger (Software Company)
Child-Specific Pattern Collections:
Abacadabra (Could not find direct link, but available on major sites like sewingpatterns.com)
Izzy and Ivy
Jona G
Oliver + S
Pink Fig Patterns
Costume/Historical Pattern Collections:
Buckaroo Bobbins
Heirloom Pattern Collections:
Bonnie Blue Designs
Chery Williams (Could not find direct link, but available through multiple online retailers)
Collars, Etc
Creative Needle (Could not find direct link, but available through multiple online retailers)
Creations by Michie
Ginger Snaps Designs
Petite Poche (Could not find direct link, but available through multiple online retailers)
Primrose Lane
Sew Baby
Treasures of the Past (Could not find direct link, but available through multiple online retailers)
Wearable Art Pattern Collections:
Design & Sew by Lois Ericson (Could not find direct link, but available through multiple online retailers)
ReVisions by Diane Ericson
This list will be a work in progress - feel free to message me on twitter @pixiepattern or email at pixiepattern@gmail.com if you have a company to add!