craigslist - craigslist provides local classifieds and forums for jobs, housing, for sale, services, local community, and events
Backflip - Selling your electronics just got easy
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.
Whatnot - The safest place to buy & sell collectibles
Facebook Marketplace - Marketplace is a convenient destination on Facebook to discover, buy and sell items with people in your community.
Experify - Connecting you to owners of products for honest opinions.