Somewhere Over the Rainbow by Israel Kamakawiwo'ole "Iz"

... one of the first that I learned... capo 5th fret

Here is Israel himself singing
http://www.youtube.com/watch?v=6ZqPLxCDLs4&feature=fvsr

Lesson by Marty Schwartz
http://www.youtube.com/watch?v=MrpUi0r548s