Run by Jonathan Kennedy of HeyCarson, Shopify Entrepreneurs is one the largest and most active ecommerce communities on the internet. With over 100,000 members, join this community to talk about all things ecommerce across every kind of topic.
Alex Fedotoff runs a Facebook group with nearly 50,000 members dedicated to intermediate-advanced Facebook advertisers and eCommerce entrepreneurs, who are spending $5,000 - $1,000,000+ per month on ads. If that's you, this might be the right place to pose problems and learn from marketers.
Join the r/Dropship subreddit community to discuss the business of dropshipping, from the entrepreneur side of the table. It's a great place to share resources, solve problems and have serious discussions on issues that other entrepreneurs face.
While not specifically about ecommerce, r/smallbusiness is a great place to ask questions and learn from others who are starting, owning and growing a small business.
The Ecommerce Group run by John Lawson is a slightly niche group with around 8,000 members. Join in to discuss strategies and tactics that can help you maximize profits with your Amazon, Shopify and Ecommerce business.
Richard Lazazzera of A Better Lemonade Stand runs Ecommerce Entrepreneurs. With close to 50,000 members, the Facebook group is one of the largest forums for discussion, learning, and growth on Shopify, ecommerce, digital marketing, Adwords, SEO, SEM, web analytics, content, CRM, etc.