"Been there, done that".

Others:

BTDTGTTS "Been there, done that, got the T-shirt".
IMHO "In my humble opinion"
IMNSHO "In my not-so-humble opinion"
BTW "By the way..."
FLAPS "Friendly local auto parts store" (VW list only?)

God knows where some of these started, although such acronyms have
been floating about the internet since the beginning.  Military use
gave us a few gems as well, some of which are ubiquitous in computers:

SNAFU : "Situation normal -- all f*cked up" (even in most dictionaries!)
FUBAR (more often spelled "foobar" and "foo"): F*cked up beyond all
  recognition"

There are some Science-fiction ones, too:

TINSTAFL: "There is no such thing as a free lunch"

TLA's and their long brethern have pervaded the computer world like so
many viruses, ever since ol' IBM was born from the the old Hollerith
cards and the first computers got named things like "ENIAC" (Electronic
numerical integration analog computer??) and MANIAC.  Even some languages
like BASIC are acronyms (beginners all-purpose instruction code).

I guess VW was one of the first two-letter acronyms.

Malcolm