I had mistakenly started a similar thread in another forum, but I'll re-post a few.
Some have been made popular by the Dilbert comics... thank Scott Adams:
PHB - Pointy-Haired Boss
PFY - Pimply-Faced Youth (usually referring to a young tech or intern)
Chat rooms have their own set of both acronyms and emoticons; in fact I did my college thesis in Interpersonal Communications on the topic of relationships that are built on line without the non-verbal cues, and how emoticons and acronyms make up for non-verbal interactions. Some include:
BBS - Be Back Soon (this is a relatively new one, BBS used to mean Bulletin Board System in the online community)
ROFL - Rolling on floor laughing
ROFLMAO - Rolling on floor laughing my a** off
PMSL - P*ssed MySelf Laughing
IMHO - In My Humble Opinion
... The other interesting thing happening (and should probably be a new thread) are the new colloquialisms that the information age has provided, reflecting current pop-culture and trends. Stuff like:
"Just google for .... " (google now being used as a verb for using the google search engine to find information)
"Text me..." (referring to text messaging on cell phones)
Just my $.02
"In order to start solving a problem, one must first identify it's owner." --Me
--Greg