Great point.
I'll rattle off a few I know:
The Test Prep Companies
TBR - The Berkeley Review
TPR - The Princeton Review
TPRH - The Princeton Review Hyperlearning
EK - Examkrackers
NS - NextStep
KA - Khan Academy
UWorld - USMLEWorld
The MCAT
CP - Chemistry and Phyisics Subsection
BB - Bioology and Biochemistry Subsection
CARS - Critical Analysis and Reading Subsection (aka Verbal Comprehension)
PS - Psychology and Sociology Subsection
Terms
SB - Section Bank, usually provided by AAMC. Full of practice questions.
FL - Full Length practice exams. Can be third party or AAMC
The Organizations
AAMC - American Association of Medical Colleges
AMCAS - American Medical College Application Service (MDs)
AACOMAS - American Association of Colleges of Osteopathic Medicine Application Service (DOs)
You'll see often in signatures:
1 - Primary applications sent out
2 - Secondaries received and/or sent out
II - Interview Invites
A - Acceptances
WL - Waitlists
R - Rejections