I find that most of the songs on Ultimate Guitar can be transposed up or down a step into a nicer, more uke friendly key. Personally I love to play anything by City and Colour
it's all about music theory (chord notes are the same, but positions are different), you can play all the uke songs you want on a guitar Sometimes you'll have to change the key, but that's all!
if you capo your guitar on the fifth fret (assuming standard EADGBe tuning), then your 4 highest pitched strings will be the same as a Low-G ukulele. Hope that helps anyone!