As I mentioned in this thread, I think it would be useful for those of us with varying levels of skill in Italian to become more familiar with popular written abbreviations for commonly used expressions. In English, I'd put BTW (by the way), IMO (in my opinion), AFAIK (as far as I know), etc. in this category.

In that other thread Alessandra mentioned TVB and SMS. What are some others?

On the Web, Italians usually use the English abbreviations, with one exception: about ten years ago LMAO was commonly substituted with MRAIC, which is its exact translation, which I can't write here because bad words are against the rules.
In proper writing abbreviations are to be avoided, but kids (and not kids anymore) tend to use often "SMS speak", which includes not only abbreviations but also letter substitution. Although I know of people my age using them, I honestly can't even read them, I have been looking on the web for a vocabulary but I coldn't locate any.

Not commonly used expressions but I find the following list of most used words in Italian interesting. From the About.com Italian Language website:

Italian SMS Abbreviations

anke: anche
c sent: ci sentiamo
cmq: comunque
dm: domani
dp: dopo
dr: dire
dv 6: dove sei
dx: destra
frs: forse
ke: che
ki: chi
km: come
kn: con
ks: cosa
mmt+: mi manchi tantissimo
nm: numero
nn: non
prox: prossimo
qlk: qualche
qlks: qualcosa
qkl1: qualcuno
qnd: quando
qndi: quindi
qnt: quanto
qst: questo
rsp: rispondi
scs: scusa
sl: solo
smpr: sempre
sms: messaggio
sn: sono
spr: sapere
sx: sinistra
sxo: spero
t tel + trd: ti telefono + tardi
trnqui: tranquillo
trp: troppo
tvtb: ti voglio tanto bene
vlv: volevo
xché: perché
xciò: perciò
xh: per ora
xò: però
xsona: persona
xxx: tanti baci
-male: meno male
+ - x: più o meno per

ROFLMAO

quote:

On the Web, Italians usually use the English abbreviations,

I didn't realize that, Alice. Thanks.