There are a couple of sources for free NAF sheet flute online.
I highly recommend Flute Tree. This site by Robert Gatliff provides the notes for many songs online. The best part is that you can choose how you want to view the notes and the fingering your flute is using so that the tablature matchs the fingering of your flute. If you don't read flute tab, then you can choose the "piano roll" version, which gives a real nice representation of the note timing for non musical trained folks.
There are several Yahoo Groups focused on NAF Sheet music. You'll need to join the groups to view and download the posted sheet music files. If you don't want to receive the emails you can setup your yahoo user account to read the messages online.: