"Into the Sunshine" by Julia Nunes
I was recently introduced to Julia Nunes' music and have been happily frolicking through her YouTube archives since. Oh how I love the sound of a voice that hasn't been produced to death! The combination of a ukulele, guitar, and vocal layering here results in a wonderfully upbeat song that won't get out my head.
I also recommend checking out "The Debt," which involves some pretty badass vocal percussion.