Without further ado—
AAP: American Association of Publishers.
AAR: Association of Authors' Representatives.
ALA: American Library Association.
ARC/ARE: Advance reading copy (or "advance reader's edition"). It's exactly what it sounds like: an early, unfinished copy of a book distributed to reviewers, buyers at accounts, and other people who need to read a book before it goes on sale. It generally has a cover and marketing/publicity information, which distinguishes it from a galley.
BEA: Book Expo America, the premier American trade show for commercial book publishers.
F&G: Folded and gathered sheets, an unbound collection of sample pages from a book used during the sales process. Almost exclusively used for children's books.
FOS: Front-of-store, referring to co-op placement.
HC/CL: Hardcover book.
ISBN: International standard book number.
MM/PB/PPB: Mass market paperback book.
MS: Manuscript (generally unbound).
MTE/MTI: Movie tie-in edition. A reissue of a book set to coincide with the release of a film based on that book (generally with new cover art taken from the movie).
NDA: Non-disclosure agreement.
OS/OSD: On-sale date.
P&L: Profit-and-loss statement, a measure of a book's overall contribution to the house's revenue (both positive and negative).
POD: Print on demand, a method of printing individual books meant to save cost on and increase availability for titles with print runs too small to succeed under the traditional publishing model.
TP/TR/QP/QPB: Trade paperback book.
TPO: Trade paperback original (i.e. a book initially published as a trade paperback, not as a hardcover).