Here are some sources for music to play on the Ukulele that are available online.
* A collection of Songbooks from the TUSC.
* A Collection of songbooks from ‘Brighton Ukulele Sundays’.
* An online songbook from Richard G, a member of AUAS.
* A collection of songs from the Ukulele Boogaloo.
* A whole host of ukulele Songbooks at Chordie.
Alternatively start to make your own songbooks from some of your favourite musicians, you can always look up the guitar chords and adapt them, this is one of my favourite ways of finding songs to play around with.