Examples of silos that allow importing and exporting OPML files.
YouTube allows people to export their subscriptions as an OPML file, which can then be used to subscribe any news reader to the channels they are subscribed to.
Many silo-based feed readers support OPML import/export as well as OPML subscription.
- dobrado allows import of subscriptions through OPML
- TinyTinyRSS supports OPML import and export via Settings -> Feeds -> OPML
In the context of IndieWeb, the idea of OPML could be interesting as a representation of whom you follow. Since it is supported by a variety of sources, It could be a good candidate to solve the "how do you discover people" question.
The advantage of using OPML is its support, however, like RSS, the standard has some limitations.
Some feed readers also support OPML subscriptions which allow users to subscribe to hosted copies of OPML files. Any changes to the OPML file are synced with the reader as new sources are added. (Compare this with importing a static OPML file that will never change.) Examples:
Sharing via OPML
If you want to show to the world who you follow, you can share an opml file on your website.
List of sites doing it: