Here is a list of my favorite tune books. (There are more out there, but these have been on my bookshelf for years.) Many of the tunes in these books are played for contra dances and English and Scottish country dancing. Note that some of these books may be out of print, but perhaps, in this day and age, they appear in electronic formats? Try searching the titles and/or their authors’ names on the Internet for more information.
Barnes, Peter, English Country Dance Tunes, A Collection of 303 Commonly Used English Dance Melodies, 1986, but recently updated. Theres also now a Volume II, of mostly original tunes. (I prefer sticking with public domain tunes.)
Keller, Kate Van Winkle and Ralph Sweet, A Choice Selection of American Country Dances of the Revolutionary Era 1775-1795, Country Dance and Song Society, Northampton, MA, 1976.
Kennedy, Peter, The Fiddlers Tune Book (I & II), Hargail Music Press, Saugerties, NY, 1954. These two small but wonderful volumes have reels, jigs and waltzes (no), leaving the harmony up to your imagination. Note: These two volumes have been updated to include and both are combined into one volume, now published by David Mallinson Publications. It’s easy to find on the Internet.
Matthiesen, Bill, The Waltz Book, 1992 and out. There are three or four volumes now, all of just waltzes.
Miller, Randy and Jack Perron, New England Fiddlers Repertoire, Fiddlecase Books, Peterborough, NH, 1983. (Note: In the handwritten version of this book, the authors left out pickups at the beginning of many tunes to draw the bar lines easily. There is a typeset edition now that may includes the pickups now.)
Raven, Michael (ed.), One Thousand English Country Dance Tunes (2nd ed, 1999); ISBN 0-906114-31-4. And they are not kidding! Contains lots of very old tunes from The English Dancing Master (1651) and more. I bought this in England, so it may take a while to ship to the US. See what Amazon.com can do.
___, The Complete Works of O’Carolan, Ossian Publications, 1984; ISBN 0-946005-16-8. Just O’Carolan’s tunes, no.
Sweet, Ralph, The Fifer’s Delight, published by the author, revised 1981. The tunes are crammed in, but there’s a lot of good stuff inside.
1,000 Fiddle Tunes, published by M. M. Cole, ISBN 0-8471-0450-8. Lots of good tunes. My copy was typeset with the staves quite close together; perhaps an updated edition is available that spaces them further apart.
As for electronic tune sources on the Internet: I don’t necessarily recommend them. Aside from numerous typos, you need to be careful regarding notey-ness and closeness of version to what musicians of this genre know. Browser, beware.