These can all be found from the Links that Malcolm sugessted but I thought I would mention them:
Tha ABC Home Page: http://www.gre.ac.uk/~c.walshaw/abc/ . This site does provide links to the other 2 I am mentioning but I find them useful so here goes.
John Chambers Tune Search: http://trillian.mit.edu/~jc/music/abc/FindTune.html
Richard Robinson's Tune Book: http://www.leeds.ac.uk/music/Info/RRTuneBk/listings.html