Musica Antigua  (not connected with MAdT in spite of the similar name!) A really well-done instrument site, which shows good pictures of instruments and offers short audios of their sound qualities.

Harmonia  Early music on public radio, plus articles and podcasts.

Early Music America  Non-profit organization for the field of historical performance in North America. Founded in 1985. Web site has a variety of resources and free recordings to listen download.