I have just created my own Drafts Action Directory that compiles many of the custom URL actions I have created and discussed previously. I only include standalone actions in this list. Standalone actions are the ones that don't require you to install other actions before you can use them.
The list allows you to browse the actions in a compact yet informative way. You can find a brief information about each action, a nicely-formatted Gist-hosted code for the URL scheme, and a link pointing to the original blog post. And if you're browsing from your iOS device, you can tap the Install link to automatically install the action on your iOS device.
Link: Drafts Action Directory