Not to hijack the listing, but USPS has these great Priority Mail padde envelopes that would probably serve your purpose. For $5 you can send up to 4 pounds anywhere in the country, and they're large so you can fit a LOT.
Here's the link:
They're free, and the post office will drop them off at your door.
ETA: if you pay for shipping online at usps.com, the tracking # is free.
==> Asugirl, you are right - the rate hike must have just happened in the past few weeks. It's $5.70 if you pay online, which is still less than any other method but not the steal it was before : (