»The Traditional Tune Archive is a World Wide Web information storing and retrieval tool dedicated to instrumental music of the past 300 years traditionally used for dancing in Ireland, Great Britain, and North America. It is a semantic system in which the meanings (semantics) of information are organized in a way that makes it possible for the web to "understand" and satisfy the requests of people and machines to use the content. Thus, the aim is to allow the semantics of traditional music pieces—their properties, historical information and musicological traits, commentaries, etc.—to be employed in an improved data structure that allows for myriad research possibilities.«
See http://tunearch.org/ and http://tunearch.org/wiki/The_Traditional_Tune_Archive:About and http://tunearch.org/wiki/A_collection_of_tunes

It's a standard MediaWiki site, with URLs of the form http://tunearch.org/wiki/:subject

It far dominantly contains articles on tunes (MB:Works), but seemingly also has some on people (composers, collectors, arrangers, etc.; MB:Artist) and tune books (MB:Series), though I haven't found anything useful about these just yet.