Andymac, as a postscript to the links posted by Masato, two books which are fairly widespread in libraries are:
Dwyer, Richard A., Lingenfelter, R. E., and David Cohen, 1964, The Songs of the Gold Rush, Univ. California Press.
Lingenfelter, Richard E., Dwyer, R. A. and David Cohen, 1968, Songs of the American West, Univ. California Press.
These books have been cited in this thread, but for convenience, above are the complete citations.
Also:
Sherwin, Sterling and Katzman, Lewis, 1932, Songs of the Gold Miners, Fisher and Son, N. Y.
Botkin, B. A., 1951, A Treasury of Western Folklore, Crown Pub.
Many others have selections. The Mudcat threads plus the DT and Forum have many useful comments and additions and add up to a good collection.
The American Memory website (see post by Masato, above) has a lot of material, some of it in the form of interviews. If you have the time and the interest, put a general term like 'miner' in their search blank, and literally thousands of items become available, including pictures, reminiscences, songs, mining regulations, etc. To cut the listing, try modifiers like 'California,' etc. Their collections will give you the grass roots background not only for the California Gold Rush, but the Klondike and Alaskan and western US gold "stampedes" as well.