craigslist - craigslist provides local classifieds and forums for jobs, housing, for sale, services, local community, and events

Swell.is - Customizable, API-first ecommerce platform for innovative brands, startups, and agencies.

Bedpage - Bedpage is a classified ad posting a website that comes as the alternative to Backpage and offers almost all the major services to post for multiple categories.

Vendure - Open-source headless e-commerce framework for developers

Facebook Marketplace - Marketplace is a convenient destination on Facebook to discover, buy and sell items with people in your community.

Shopify - Shopify is a powerful ecommerce platform that includes everything you need to create an online store and sell online. Try it free for 14 days.