GCstar is a free open source application for managing your collections. Detailed information on each item can be automatically retrieved from the internet and you can store additional data, such as the location or who you've lent it to.
Catalog your books, movies, music, software, toys, tools, electronics, & video games in a nice interface. Import all your stuff onto your digital shelves using your Mac’s iSight webcam, our wireless barcode scanner, or your keyboard.
Home Inventory, a Mac App Store editors' choice, is a critically acclaimed and easy to use app for creating catalog of your possesions using your MacDiscontinued
It seems like this app is being replaced by Under My Roof (same developer) with added support for iOS and a new UI. "After 16 years, Home Inventory will continue to be supported but will not receive new features."