Dutch: an auction where more than one of an item is available.
Feedback: positive or negative comments left about other users on eBay.
Mint: in perfect condition.
Non-paying bidder: a bidder who wins an auction but does not then go on to buy the item.
PayPal: an electronic payment method accepted by most sellers.
Rare: used and abused on eBay, now entirely meaningless.
Reserve: the minimum price the seller will accept for the item.
Shill bid: a fake bid placed by a seller trying to drive up their auction's price.
Snail Mail: the post, which is obviously very slow compared to email.
Sniping: bidding at the last second to win the item before anyone else can outbid you.
Initials & Abbreviations
BIN: Buy it Now. A fixed price auction.
BNWT: Brand New With Tags. An item that has never been used and still has its original tags.
BW : Black and White. Used for films, photos etc. CONUS: Continental United States. Generally used by sellers who don't want to post things to Alaska or Hawaii.
EUR: Euro Currency.FC: First Class. Type of postage.
GBP: Great British Pounds Currency.
HTF: Hard To Find. Not quite as abused as 'rare', but getting there.
NIB: New in Box. Never opened, still in its original box.
NR: No Reserve. An item where the seller has not set a reserve price.
OB: Original Box. An item that has its original box (but might have been opened).
PM: Priority Mail.
PP: Parcel Post.
SH: Shipping and Handling. The fees the buyer will pay you for postage.
USD: United States Dollars Currency. VGC: Very Good Condition. Not mint, but close.