"Overview of the U.S. Copyright Registration Process," by attorney Larry Guffey:
http://www.guffeylaw.com/copy-r.htm
"Warnings and Cautions for Writers - Copyright," by the Science
Fiction & Fantasy Writers of America (lots more helpful links at
the end):
http://www.sfwa.org/beware/copyright.html
A relevant Question of the Month at lawandfiction.com:
http://www.lawandfiction.com/law/column.4.html
"Your Copyright Provides the Legal Foundation for Making a Living as a Freelance Writer," by the National Writers Union
http://www.nwu.org/docs/copyrite.htm