I just wrote a big fat cover piece on Neil Patrick Harris, in which I mention his many online clips.
Here are a few.
N.P.H. and Jason Segel Sing 'Les Miz'
Dr. Horrible's Sing-along Blog
N.P.H. As the Fairy Shoe Person
Montage of Barney From How I Met Your Mother
N.P.H. As Tobias in Sweeney Todd
N.P.H. in the First Harold & Kumar
A Very Short Clip of N.P.H. and David Burtka Singing "Take Me As I Am"
From Rent at a Benefit