That link to the automotive abbreviations went directly into my bookmarks!
And "c230man" (sounds like an invitation to visit the dentist, "see tooth hurty-man") OEM actually means Original Equipment Manufacturer...
Yes, LOL means "laughing out loud". And Steve already covered IMHO, "in my humble opinion". There's also these:
ROFL - Rolling On Floor Laughing.
ROFLMFAO - Rolling On Floor Laughing My F%#*ing A@* Off.
LMAO - Laughing My A#@ Off.
FYI - For Your Information.
FWIW - For What It's Worth.
AAMOF - As A Matter Of Fact.
AIYDK - As If You Didn't Know.
ICYDK - In Case You Didn't Know.
AIIC - As If I Cared.
BTDT - Been There, Done That.
BTW - By The Way.
LNGT - Let's Not Go There.
There are more @