Lately I've been using 'Band in a Box' to learn a few new tunes.  Sometimes, I can't find the tune I want in the bb folders.  Did you know you can download tunes in midi format, import them into bb and it will automatically map the chords/melody?  (file menu>import midi).  You just need to specify which channel the melody is on, and et voila.  There are heaps of free midi tunes on the net such as:

http://www.haightashbury.org/HaightAshburyMusic/midi.html

http://www.gitpicker.com/hatfav2.html