Because you are asking for a Base set abbreviation, I'll take the assumption that you play unlimited.
Base - B
Jungle - J
Fossil - F
Team Rocket - TR
Gym Heroes - GH
Gym Challenge - GC
Neo Genesis - NG
Neo Discovery - NDC
Southern Islands - SI
Neo Revelation - NR
Neo Destiny - NDT
Legendary Collection - LC
WotC Black Star Promos - WP
Expedition - EX
Aquapolis - AQ
Skyridge - SK
WotC Best Promos - WB
RubySapphire - RS
Sandstorm - SS
Dragon - DR
Team Aqua vs Team Magma - AM
Hidden Legends - HL
Fire Red/Leaf Green - RG
EX Trainer Kit - TK1
OP Series 1 - OP1
Team Rocket Returns - TRR
Deoxys - DX
Emerald - EM
Unseen Forces - UF
OP Series 2 - OP2
Delta Species - DS
Legend Maker - LM
EX Trainer Kit 2 - TK2
OP Series 3 - OP3
Holon Phantoms - HP
Crystal Guardians - CG
OP Series 4 - OP4
Dragon Frontiers - DF
Power Keepers - PK
OP Series 5 - OP5
Diamond and Pearl - DP
Mysterious Treasures - MT
OP Series 6 - OP6
Secret Wonders - SW
DP Trainer Kit 1 - TK3
Great Encounters - GE
OP Series 7 - OP7
Majestic Dawn - MD
Legends Awakened - LA
OP Series 8 - OP8
Stormfront - SF
Platinum - PL
Rising Rivals - RR
OP Series 9 - OP9
Supreme Victors - SV
Arceus - AR
Rumble - RU
HeartGold SoulSilver - HS
Unleashed - UL
Undaunted - UD
Triumphant - TM
Call of Legends - CL
Nintendo Black Star Promos - NP
DP Promos - NDP
HGSS Promos - HSP
And there, my friend, is every abbreviation, from Base Set, all the way to now.
To be honest, I knew there was a lot of sets, only after typing it all did I realize. "
Holy snap. There are a lot of sets".
Anyway, hope I helped you.
EDIT:
Erm... I guess Cris edited his post to make mine moot... :/ Ah well. At least you'll have two lists to look at in case you think one of us is lying.