Yep B&M means brick and mortar or in-store. Here's a good list for ya.
Common abbreviations:
- A -
AFAIK - As far as I know
AFK - Away from keyboard
AR - After rebate
- B -
B&M - Brick and mortar store (A physical retail store as opposed to an online merchant)
B1G1 or BOGO - Buy one get one free
BB - Best Buy
BF - Black Friday
- C -
CC - Circuit City
CC - Credit card
CPN - Coupon
CSR - Customer service representative
- D -
DOA - Dead on Arrival
- E -
ER - Easy Rebates (for Staples), sometimes also used for CompUSA eRebates
- F -
FAR - Free After Rebate
FWIW - For what it's worth
FS or F/S - Free Shipping
- G -
GC - Gift certificate
GCO - Google Checkout
- H -
HD - Hot deal, Home Depot, High Definition
HSN - Home Shopping Network
- I -
IRC - Internet Relay Chat
IIRC - If I Recall Correctly
IMHO - In My Honest/Humble Opinion
IMO - In my opinion
IR - Instant rebate
- M -
MFG - Manufacturer
MFR - Manufacturer
MIR - Mail in rebate
- O -
OD - Office Depot
OEM - Original Equipment Manufacturer
OM - Office Max
OOS - Out of stock
OP - Original Poster (author of thread)
OT - Off topic
- P -
PM - Price match
PM - Private Message
- R -
RMA - Return Merchandise Authorization
- S -
SASE - Self addressed stamped envelope
S/H - Shipping and handling
- Y -
YGM - You've got mail
YGPM - You've got a private message
YMMV - Your mileage may vary
What's B&M??? 
