Richard Byrne's blog features articles about and reviews of technology teachers could use in their classroom. Though not music education specific, the resources provided could be adapted for use in the music classroom.
J.W. Pepper's online sheet music store is a great place to listen to and order new music. The music usually ships quickly from various locations around the United States. In addition, many of the pieces are available for electronic download. This feature can be important when you need sheet music immediately.
With almost 65,000 accessible sound files, Stanton's Sheet Music Listening Library is my first resource for finding the publisher's demo recordings of concert band and jazz band music.
I use tis online metronome in my rehearsals almost every day. Since it is web-based, students can use this for individual or group practice without any additional apps or hardware.
Henkjan Honing is a professor of Music Cognition at the University of Amsterdam. This blog presents articles on the human understanding of music. Some of the articles are in English while others are in German.
Alex Ross, the music critic for The New Yorker, maintains a blog featuring information about performance, books, videos and other music related topics.
Doug Butchy complies a collection of music education related online resources distributed daily. He draws from blogs, Twitter and other social media sites to collect this information. His collection of links is a great starting point for daily reading.
The Library of Congress maintains an encyclopedia of all performing arts collections they curate. This website can be used to access content from some of these collections and find information about most collections.
The Library of Congress collects digital recordings of historically significant music. Access to these recordings is free and can be used in your classroom to present this music to your students.