HomeKitty is a a crowdsourced website that collects all accessories that support the HomeKit protocol. If you want to quickly compare and find new accessories for your home of the future, there is no need to Google around hundreds of websites. Simply select the category and choose an accessory to open its official website.
At the moment, only accessories that are available for purchase are going to be accepted. Soon, we will be able to start accepting accessories that have been announced but not yet released. Each accessory will then have a badge specifying its availability.
If you live in Europe, Homekit products might be more useful. It only shows products available in the EU and is multilingual.