Covetly - Collectibles marketplace with appraisal tools
Thunkable - Powerful but easy to use, drag-and-drop mobile app builder.
Thinga.Me by Microsoft - Make virtual collections of your real stuff
MIT App Inventor - App Inventor is a cloud-based tool, which means you can create apps for phones or tablets right in your web browser.
Lofty - Trusted Marketplace for Fine Arts, Antiques and Collectibles
Bubble.io - Building tech is slow and expensive. Bubble is the most powerful no-code platform for creating digital products.