U.S. Copyright Office:
http://www.copyright.gov/
U.S. Performing Rights Organizations aka PRO's:
http://www.bmi.com
http://www.ascap.com
http://sesac.com
http://www.soundexchange.com
Education; recommended reading/viewing:
http://entertainment.howstuffworks.com/music-royalties.htm/printable
Taxi interview with Matt Hirt;
Earning Your Living with Film & TV Placements
(7 parts; Each are about 5-8 minutes long; a total of 45 minutes, but totally worth it)
Part 1 - http://youtube.com/watch?v=6FguwMMsDZA&mode=related&search=
Part 2 - http://youtube.com/watch?v=cvTStQweVVo
Part 3 - http://youtube.com/watch?v=Y_0SxBUGfKA&mode=related&search=
Part 4 - http://youtube.com/watch?v=S8kp1UK-lYg&mode=related&search=
Part 5 - http://youtube.com/watch?v=96fEPG-XdkM&mode=related&search=
Part 6 - http://youtube.com/watch?v=KO3BqT7Q7OI&mode=related&search=
Part 7 - http://youtube.com/watch?v=I8txykKpVfU&mode=related&search=
About Music Libraries:
http://www.taxi.com/transmitter/0606/headlineC0606.html
Digital literature:
http://www.digitalmusicnews.com
