Also, the Carleton Singing Knights!
Rich Girl (I love this almost more than the original)
Harder Better Faster Stronger feat. Daft Hands (poor quality, but still, it's Austin!)
Cupcake (so good)
Oxford Comma (fun fact: I can play this on my ukulele!)
Pop! Goes my Heart (the bridge at 1:46 is great)
really, I could just link to billions of their videos, because let's face it, acappella is pretty great and so is Carleton.