Many of these are in the FAQ, but here's what various abbreviations mean or stand for
AFAIK -- "As Far As I Know"
AFAICT-- "As Far As I Can Tell"
AFAL -- "As Fast As Light"
AIUI -- "As I Understand It"
AOL -- A replacement for "Me too" - as posted by many AOL users
ASB -- "Alien Space Bats" a force that can create otherwise impossible situations
ATL -- "Alternate Time Line"
BTW -- "By the way"
EFP -- "Extruded Fantasy Product" (Goodkind, Eddings, etc)
FTL -- "Faster than light"
FWIW -- "For What It's Worth"
FYI -- "For your information"
IIRC -- "If I Recall (remember) correctly"
IMAO -- "In my arrogant opinion"
IMHO -- "In my humble opinion"
ISBN -- "International Standard Book Number"
ISTR -- "I Seem To Recall"
ObSF -- "Obligatory SF reference"
OTL -- "Our Time Line"
RASF -- "rec.arts.sf"
ROFL -- "Rolling on the floor, laughing"
ROTF -- "Rolling on the floor"
RPG -- "Role playing games", like D&D (Dungeons and Dragons)
RSN -- "Real Soon Now" (== within the next decade or two)
STL -- "Slower Than Light"
WI -- "What If"
WRT -- "with respect to"
WSOD -- "Willing Suspension of Disbelief"
YASID -- "Yet Another Story ID" request
YMMV -- "your mileage may vary"
midlist-- Authors who don't make bestseller lists but put out
a steady stream of readable books over time
The Six Deadly Words -- I Don't Care About These People
The Six Deadly Words -- I Don't Care About This Book