The Library of Congress web site is the easiest and cheapest way to go. You can print out the forms you need right there, using Adobe Acrobat.

The cheapest way is to put your songs on tape, give it a name ("Spring Songs - 2001", or something like that) and copyright it as a collection. List all the individual songs as part of the collection on the copyright form and pay $20 for the whole bunch.

Publishing and copyrighting are not the same thing.