Internet Slang: M- P

M
MMORPG, MMO - Massive Multi-player Online Role Playing Game
MOTD - Message of the day
MTFBWY - May The Force be with you
MUD - Multi-User Dungeon
MUSH - Multi-User Shared Hallucination
MYOB - Mind your own business
M8 – Mate

N
N1 - Nice one, used mostly often in gaming
NE1 - "Anyone"
newbie, newb, n00b - An inexperienced user of a system or game, or an annoying person. Usually a derogatory term for someone inexperienced at a game.
NIFOC - Naked In Front Of Computer
NM - (Sometimes written N/M) Not much, Never mind or no message, used on message boards or in e-mails to indicate that everything is already said in the subject line.
n0rp - Alternate form of pr0n, intentional misspelling of porn
NP - No problem
NS - Nice shot. Used in online gaming.
NSFW - Not safe for work. Warning about content that may get the viewer in trouble with his employer or co-workers.
NVM, NVMD, or nm - Nevermind, not much

O
O RLY - Oh really?
OIC - Oh, I see
OFN - Old freaking news
OMG - Oh my god
OMFG - Oh my fucking god
OMGWTF - Oh my God what the fuck
OMW - On my way or Oh my word
ONOZ - Oh, no
OP - Original poster / Operator / Outpost
OS - Operating system
OT - Off topic
OTOH - On the other hand
OTP - On the phone or One true pairing or On The Piss

P
P2P - Peer to peer, or pay to play
PAW - Parents are watching
PEBKAC/PEBCAK - Problem exists between keyboard and chair
PITA - Pain in the arse / ass
PLMK - Please let me know
PMSL - Pissing myself laughing
POS - Piece of shit, or parent over shoulder.
POTS - Plain old telephone service
POV - Point of view
PL - Powerleveling, used in online games.
PPL - People
PTKFGS - Punch the Keys For God's Sake
pr0n - Intentional misspelling of porn
PW - Persistent World (gaming)
pwned - Intentional misspelling of owned