Bear in mind that these items may be available through other sources at better prices, but I like the one stop shop approach of an office supply store. Blank CD-Rs can be bought in bulk, often in spindles of 50, for far less than you'll pay for branded TDKs at Office Max. However, you need to remember that the discs you buy need to work in other people's burners. They seem to be the Maxell of CD-Rs. Also, if you can find a smaller envelope than the 9x12 Tyvek for shipping there, that the bubble mailer will fit into, use it.
Some traders have a hard time getting the large envelope delivered to their residence.
And many people find that manila envelopes will work just fine, but I prefer the strength of the Tyvek envelopes. Some feel that Paper Fibers can contaminate CDs. Try to avoid buying the mailers that are padded with paper fiber. Some traders feel that these can contaminate the CDs with small particles, especially since the packages seem to easily get statically charged and can rip when opening. Jewel Cases will usually not survive the shipping, and add significantly to the postage costs.