Proposed additions to the List of internet slang:

dictionary.com

edit
AKA
"also known as" [1]
Anon
"anonymous" [2]
ASAP
"as soon as possible" [3]
AWOL
"absent without leave" (from military slang) [4]
BCNU
"be seeing you" [5]
Boot
to eject a player from a server [6]
Blogger
one who writes or posts articles on a weblog [7]
BOHICA
"bend over, here it comes again" (from military slang) [8]
BRB
"be right back" [9]
BS
"bullshit" or "backstab" [10]
CU
"see you" [11]
CYA
"see ya" or "cover your ass" [12]
DIY
"do it yourself" [13]
EOL
"end of line" [14]

[15]

ETA
"estimated time of arrival" (also "edited to add") [16]
EULA
"End User License Agreement"

[17] [18]

F2F
"face to face" (that is, "in real life") [19]

[20]

FAQ
"Frequently Asked Questions" (printed with their respective answers) [21]

[22]

Frag
to kill (from fragmentation grenade; see frag) [23]
FUBAR
"fucked up beyond all recognition" (from military slang; pronounced "foo-bar") [24]
FWIW
"for what it's worth" [25]
FYI
"for your information" [26]
GTG
also "got to go" [27]

[28]

FOLDOC

edit
Admin
"administrator" (systems administrator or forum moderator) [29]
AFK
"away from keyboard" (also backronymed to "a free kill") [30]
ATM
"at the moment" [31]
B2B
"business to business" or "back to back" [32]
EOF
"end of file" [33]
Flamer
one who writes inflammatory posts, also known as an Internet Troll [34]
FOAF
"friend of a friend" [35]
FUD
"fear, uncertainty, and doubt" (the purposeful spread of misinformation) [36]
HAND
"have a nice day" [37]
HTH
"hope this/that helps" or "happy to help" [38]
IANAL
"I am not a lawyer" [39]
IDK
"I don't know" [40]
IIRC
"if I recall/remember correctly" [41]
IMAO
"in my arrogant opinion" or "I am laughing my ass off" [42]
IMHO
"in my humble/honest opinion" [43]
IMNSHO
"in my not so humble opinion"

[44]

IMO
"in my opinion"

[45]

IOW
"in other words"

[46]

IRC
Internet Relay Chat

[47]

IRL
"in real life"

[48]

Lag
"latency" (whether due to a server problem or the server-client connection)

[49]

Lamer
a know-nothing

[50]

LMAO
"laughing my ass off" (can be parodically extended to "LMAOnade", etc) [51]
LOL
"laughing out loud" or "lots of laughs" [52]

(For other variations of the word LOL, see LOL (Internet slang))

Lurker
one who frequents a message board without participating in discussions

[53]

MOTD
"message of the day" [54]
MUD
"Multi-User Dungeon" [55]
MUSH
"Multi-User Shared Habitat" [56]
MYOB
"mind your own business" [57]
Newb
"newbie"

[58]

NIFOC
"naked in front of computer" [59]
OIC
"oh, I see" [60]
Op
"operator" (a moderator) [61]
OS
"Operating System" [62]
OTOH
"on the other hand" [63]
PEBKAC
"problem exists between keyboard and chair" [64]
PITA
"pain in the ass" [65]
PLMK
"please let me know" [66]
Rehi
"hello again" [67]
RL
"real life" [68]
RSN
"real soon now" (used sarastically) [69]
SNAFU
"situation normal all fucked up" (from military slang) [70]
SOL
"shit out of luck" [71]
TIA
"thanks in advance" [72]
TINC
"there is no cabal" (a term discouraging conspiracy theories) [73]
TLA
"three letter acronym" [74]
TOS
"terms of service" [75]
Troll
one who deliberately stirs up trouble or posts false information [76]
TTFN
"ta ta for now" [77]
TTYL
"talk to you later" [78]
TYT
"take you time" [79]
Wares (also warez)
illegally obtained software [80]
WB
"welcome back" [81]
WOMBAT
"waste of money, brains, and time" [82]
WRT
"with respect (or regards) to..." [83]
WTF
"what the fuck?" (less commonly, but equally validly, "who/what/when/where the fuck?") [84]
WTH
"what the hell?" [85]
WYSIAYG
"what you see is all you get" (suggesting that software is incomplete) [86]
WYSIWYG
"what you see is what you get" (pronounced "wizzywig"; printed output will look identical to its screen representation) [87]
YMMV
"your mileage may vary" (used as a disclaimer for an opinion) [88]