Market / catalog for free non-ad apps? Is there a market or catalog dedicated to apps (open source or not) that are free and don't contain ads? I find them hard to search for on the standard markets.

Please note: I'm not looking for a way to block ads in apps, or some other way to circumvent ads that the app developer wants to show. I'm looking for free apps that don't have ads by design.
F-droid is an open source (and free) market of Android apps. As far as I remember, they are ad free (or there is at least an in app option to filter the apps).