Internet Auctions like Ebay
Efficient shipping procedures can say significant time and money.
Scale I would suggest efficient shipping starts with a good digital scale. You can buy one for about $40.00 (Maybe that should be one of the Ebay purchases you make to build your feedback rating.) With a good scale you will be able to quote flat rate shipping in your auctions. This means buyers can pay you immediately after your auction ends without any contact from you.
Boxes. One of the reasons USPS priority mail is so popular is that you get free boxes. The Post Office has also adjusted their rates so that attempting to save money by using Parcel Post is impossible. Unless you get a lot of pleasure dumpster diving for free boxes, I think it is the way to go.