Websites can programmatically define a blogroll using OPML. These blogrolls help people who read your blog discover other websites you think are worth promoting.

A diagram showing how an OPML blogroll can link to RSS feeds, which in turn can each link to another OPML blogroll, and so-on This project maps connections between websites, web feeds (RSS, Atom, and JSON feeds), and OPML blogrolls. The size and interconnectedness of the network can be tracked over time. Exploring the network can help you discover new websites recommended by bloggers you already follow.

“Always-on” RSS and OPML menus for the Windows taskbar