Amazon FBA is easily my most profitable platform as far as online business goes. Amazon makes it easy, allowing you to simply ship them products you would like to sell. Amazon then handles the leg work while you get paid.
I have been selling on eBay for over a decade and absolutely love it. This is where it all started, and today I am a Top Rated Seller on the platform. I specialize in Clothing, Video Games, Electronics and more.
Poshmark is the newest of the three platforms featured on this site, but it is growing rapidly and can be very profitable for sellers. Poshmark also just expanded to feature Women's, Men's and Children's clothing.