I found the list below in the FAQ forum, but it was posted in 2008 so there are probably a few new ones since then. I looked for a complete acronym list (carseat specific) but couldn't find one. I probably am just missing it! Could someone link to the list or, if a more complete one doesn't exist, perhaps add to the one below?
AO(E)-Alpha Omega (Elite)
BB-Backless Booster
BPB-Belt Positioning Booster
BR-Britax Frontier
BRU-Babies R Us
BSC-Belt Shortening Clip
Bucket-Infant Carrier
BV-Boulevard/Britax
CA-Complete Air
CALX-Complete Air LX
CMVSS-Canada Motor Vehicle Safety Standard
CCO - Combi Coccoro
CPSA-Child Passenger Safety Advocate
CPS-Child Passenger Safety
CPST-Child Passenger Safety Technician
CR-Child Restraint
D-RING-Part of the Britax extender strap for tethering rear-facing
DC-Decathlon/Britax
DOM-Date of Manufacture
EB-Eddie Bauer
EH-Extended Harnessing
EPS-Expanded Polystyrene Foam
ERF-Extended rear-facing
EFTA-Evenflo Triumph Advance
EFTA65-Evenflo Triumph Advance 65
FF-Forward-Facing
FMVSS-Federal Motor Vehicle Safety Standard
FP-Fisher-Price
FPSE-Fisher-Price Safe Embrace
FPSVB-Fisher-Price Safe Voyage Booster
FPSVD-Fisher Price Safe Voyage Deluxe
FR-Britax Frontier
FR85-Britax Frontier85
GAB-Graco Air Booster
GN-Graco Nautilus
GO-Safeguard GO Seat
GSR-Graco Snugride
HBB-high back booster
HWH-High Weight Harnessed
KF-Chicco Keyfit infant seat
LATCH-(L)ower (A)nchors and (T)ethers for (Ch)ildren
LBB-Low Back Booster
LBP-Lap Belt Positioner; also Long Belt Path
LC-Learning Curve
MA-Marathon/Britax
MCP-Maxi-Cosi Priori
MM-Mia Moda
MR-MyRide Graco
OHS-Overhead Shield
PW-Parkway/Britax
PWSG-Parkway Safeguard Britax
RA-Roundabout/Britax
RC-Recaro Como
RF-Rear-Facing
RN-Radian (Sunshine Kids)
RS-Recaro Signo
RSTV-ride safer travel vest
RYS-Recaro Young sport
SFO-Safety First Onboard
SG-safeguard
SIP-Side Impact Protection
SK-Sunshine Kids(maker of Radian)
SKJP-Sunshine Kids Juvenile Products
SL-Super LATCH (on some Radian seats)
SBP-Short Belt Path
SR-SnugRide/Graco
SR22/32/35-Graco Snugride
SSK-Sunshine Kids
SS1-SafeSeat/Graco
SS2-Safeseat 2/Graco
SR/C Starriser/ Britax
TA-Tether Anchor
TA-Evenflo Triumph Advance
TC-Transport Canada
TRU-Toys R Us
TSIP-True Side Impact Protection (Britax)
TT-Top Tether
UAS-Universal Anchorage System (also Canadian term for LATCH)
WM-Walmart
XTSL-Radian XTSL(Super LATCH)
AO(E)-Alpha Omega (Elite)
BB-Backless Booster
BPB-Belt Positioning Booster
BR-Britax Frontier
BRU-Babies R Us
BSC-Belt Shortening Clip
Bucket-Infant Carrier
BV-Boulevard/Britax
CA-Complete Air
CALX-Complete Air LX
CMVSS-Canada Motor Vehicle Safety Standard
CCO - Combi Coccoro
CPSA-Child Passenger Safety Advocate
CPS-Child Passenger Safety
CPST-Child Passenger Safety Technician
CR-Child Restraint
D-RING-Part of the Britax extender strap for tethering rear-facing
DC-Decathlon/Britax
DOM-Date of Manufacture
EB-Eddie Bauer
EH-Extended Harnessing
EPS-Expanded Polystyrene Foam
ERF-Extended rear-facing
EFTA-Evenflo Triumph Advance
EFTA65-Evenflo Triumph Advance 65
FF-Forward-Facing
FMVSS-Federal Motor Vehicle Safety Standard
FP-Fisher-Price
FPSE-Fisher-Price Safe Embrace
FPSVB-Fisher-Price Safe Voyage Booster
FPSVD-Fisher Price Safe Voyage Deluxe
FR-Britax Frontier
FR85-Britax Frontier85
GAB-Graco Air Booster
GN-Graco Nautilus
GO-Safeguard GO Seat
GSR-Graco Snugride
HBB-high back booster
HWH-High Weight Harnessed
KF-Chicco Keyfit infant seat
LATCH-(L)ower (A)nchors and (T)ethers for (Ch)ildren
LBB-Low Back Booster
LBP-Lap Belt Positioner; also Long Belt Path
LC-Learning Curve
MA-Marathon/Britax
MCP-Maxi-Cosi Priori
MM-Mia Moda
MR-MyRide Graco
OHS-Overhead Shield
PW-Parkway/Britax
PWSG-Parkway Safeguard Britax
RA-Roundabout/Britax
RC-Recaro Como
RF-Rear-Facing
RN-Radian (Sunshine Kids)
RS-Recaro Signo
RSTV-ride safer travel vest
RYS-Recaro Young sport
SFO-Safety First Onboard
SG-safeguard
SIP-Side Impact Protection
SK-Sunshine Kids(maker of Radian)
SKJP-Sunshine Kids Juvenile Products
SL-Super LATCH (on some Radian seats)
SBP-Short Belt Path
SR-SnugRide/Graco
SR22/32/35-Graco Snugride
SSK-Sunshine Kids
SS1-SafeSeat/Graco
SS2-Safeseat 2/Graco
SR/C Starriser/ Britax
TA-Tether Anchor
TA-Evenflo Triumph Advance
TC-Transport Canada
TRU-Toys R Us
TSIP-True Side Impact Protection (Britax)
TT-Top Tether
UAS-Universal Anchorage System (also Canadian term for LATCH)
WM-Walmart
XTSL-Radian XTSL(Super LATCH)