The Society of Professional Consultants

Laura Burford's Consulting Guide:
https://www.laurasconsultingguide.com/

How to Land the Best Speaking Opportunities - Steve Markman
https://markmanspeaker.com/custom-advisory-services/solo-practitioner/

Consulting Q & A:
https://consulting.wiki/consulting-qa/

Art of Consulting:
https://consulting.wiki/art-of-consulting/

Process Street Consulting Resources:
https://www.process.st/small-business-resources/

David A Fields Consulting Coach:
https://www.davidafields.com/

Michael Zipursky's Consulting Success:
https://www.consultingsuccess.com/

The Complete Guide to Starting a Consulting Business (from HubSpot):
https://blog.hubspot.com/sales/consulting