DEO: Demon's Eternal Oblivion
RAW - Rules as written (a literal reading of the phrasing)
IMS/IYS
AC - Arcane Connection
RDT - Range, Duration, Target
(The 15 Arts)
TeFo - generic reference to Technique/Form of a spell effect
Thank you all for contributing, especially Furion for his list.
I'll edit the first thread to incorporate te ideas you have posted and those you will post in the future. I'll also arrange them somehow (alphabetically? Alphabetically but first divided into categories).
something I've been wondering about: The green smilie - what exactly does it stand for?
I added
IC
OOC
(GotF is technically not "Germany", but the Rhine Tribunal supplement).
You could probably go down the list of books, in print and out, and figure out the abbreviation for each one.
Its the sound it sounds like when said as written. Short vowel though.
If someone posts something that isnt really good but not really bad either, i might comment that its meh...
Might also be used as a "meh, who cares"...
Of course, "locally" its one of those "all in one" words... :mrgreen:
Depending on the context, "meh" can mean "who cares?" (as DW says), or "I'm not very impressed/excited about that", or "either way, no matter to me".
Think about something along those lines, shrug your shoulders, and say "meh". That's it. 
Just a slight correction there: the Berk List is not closed, but neither had it been very active lately.
Thanks, JeanMichelle, for posting these!
Some of us use;
RoP: TD and RoP: TI for The Divine and The Infernal, respectively...
I wouldn't mind. But I do not know if I have any rights concerning this list.
If your text, in its entirety, is exclusively composed of wording of your own making, the possibility of copyright infringement is evanescent, if at all. Except for similar compilations produced by other fans, such as the list of M&S bonuses, I do not remember a comprehensive list of abbreviations of ArM-related material ever having been published under fifth edition to date, so the context of your text, too, is unlikely to be subject to law suits.
If you are unsure about the wiki page, you could also compile a PDF and send it to Atlas Games to be hosted in the section of fan-created contributions instead. That way, the availability of the document would be more prominent, but harder to maintain and update.
Use it then
HA - Hermetic Age, the number of years of experience after gauntlet (see PG)
PG - Post Gauntlet, referring to a mage's experience since apprenticeship (see HA)
(Been waiting a long time to use that word, huh?) 
Aeons.
surprised this wasn't mentioned:
ysmv - your saga may vary - implying that a rules/world interpretation or judgement from SG or Troupe is possible or even expected
thanks. added.
S&M bonuses = Shape & Material bonuses
Also minor nitpick: It should be GotF.
added