Hi! I'm new here, and love this site. I had to jump in here on this topic as this is what I did for 23 yrs.
You can send a padded mailer media rate. All sound recordings, books, bound printed matter can be sent media rate.
Keep in mind though, that this is the lowest class of mail there is. Also can be opened for inspection where first class and priorty cannot be opened by anyone other than postal inspectors.
Priority flat rate envelopes and boxes save a ton especially when sending overseas to our soldiers. With free boxes, it is a really great bargain.