ASCAP – American Society of Composers, Authors and Publishers (music related)
Christian Copyright Licensing International – For music lyric permissions
Publishing Law Forum – I highly recommend this site.
Copyright Clearance Center – Register your for work for use by others or to obtain permission
The Copyright Web Site - The best copyright resource on the internet
Buy the book, The Copyright Handbook: How to Protect and Use Written Works 10th Edition by Stephen Fishman, Nolo Press.
Buy the book, The Copyright Permission and Libel Handbook : A Step-By-Step Guide for Writers, Editors, and Publishers(Wiley Books for Writers) by by Lloyd J. Jassin and Steve C. Schecter, John Wiley & Sons Publishing.
Buy the book, Kirsch’s Handbook of Publishing Law : For Author’s, Publishers, Editors and Agents, by Jonathan Kirsch, Silman-James Press.