Google is your friend
I typed in "lung sounds" and found many helpful links.
For some basic breath sounds, click on the left menu bar (bronchial, vesicular, etc)
This is another good site. Be sure to listen on speakers first so you can adjust the volume as needed. I listened once with my headphones and I really hurt my ears :P
Does you school have a video or audio library for nursing students? I would check that out to see if they have any samples too.
I am a 2nd year student and just last week ascultated newly developed crackles on a patient. It was my first time finding something like that and it felt so good!