OPML Search is a search engine designed to search within a centralized user contributed OPML files database. Users can upload their own OPML files, the system adds them to the database and it’s searchable for the benefit of the entire community.

Don’t know what OPML is? OPML (Outline Processor Markup Language) is an XML format for outlines (originally developed by Radio UserLand). It has since been adopted for other uses, the most common being to exchange lists of RSS feeds between RSS aggregators. Basically, when you export or import RSS lists in aggregators this is the file format to use.