I sold a readymade logo design at BrandCrowd
It's fun to develop logos for imaginary companies and it's more exciting if you could sale your concepts for money. When I am not designing for my clients - I create arbitrary ready-made logo designs for concept development for new projects. And sometimes I showcase these designs at pre-made logo marketplaces.
Brandcrowd (BrandStack earlier) is such a great brand marketplace where designers can sale their ready-made logo designs and mascots and prospective clients who is in need of such designs and doesn't have much time to develop a fresh logo for their organizations can buy and download them instantly.
Open layer was inspired by impossible design by Escher, you can read more about this logo design here
Earlier I sold other ready-made logo designs at IdentityCrowd and logoMyWay.