One of the most popular posts on iOS Developer Tips is The Complete Tutorial on iOS/iPhone Custom URL Schemes. On a related note, Arte Merritt wrote to tell me about GotSchemes, a searchable database of URL schemes.
Each URL includes information about the provider (app/company), bundle ID, App ID and whether it’s been confirmed to be supported on iOS and Android.
You can also contribute your own custom URL schemes via an application:
The app scans the iOS apps in the iTunes folder on your computer, detecting schemes and uploads them to GotSchemes.com. The application works on both Mac and PC computers, provided a Java Runtime Environment exists.