Don't get too excited just yet: this is a raw list of digitized books that Google's webcrawlers have found, rather than an archive. Some of the above are available to the general public online, some are not. Most have been digitized and put online not by Google, but by academic or commercial institutions; and some of these place restrictions on access.

With due respect to Jim, an edited list, checked to see which links actually lead to available resources, would be more helpful; and some of the above aren't collections of Scottish songs at all, though all contain enough Scottish references to come up in a Google search.