The list is ordered from the oldest to the most recent announcement made by the Riot staff regarding skin sales.

Pre-Seasons Seasons
Pre-Season One Season One
Pre-Season Two Season Two
Pre-Season Three Season Three
Pre-Season Four Season Four
Pre-Season Five Season Five
Pre-Season Six Season Six
Pre-Season Seven Season Seven
Pre-Season Eight
Early Sales


Period Sales Link
November 8
2013
November 11
2013
GravesSquare Jailbreak Graves [S|L] - 50% off
VeigarSquare Veigar Greybeard [S|L] - 50% off
PantheonSquare Ruthless Pantheon [S|L] - 50% off
[1]
November 12
2013
November 15
2013
VarusSquare Blight Crystal Varus [S|L] - 50% off
LuluSquare Dragon Trainer Lulu [S|L] - 50% off
Xin ZhaoSquare Commando Xin Zhao [S|L] - 50% off
[2]
November 15
2013
November 18
2013
IreliaSquare Infiltrator Irelia [S|L] - 50% off
XerathSquare Runeborn Xerath [S|L] - 50% off
CaitlynSquare Resistance Caitlyn [S|L] - 50% off
[3]
November 19
2013
November 22
2013
NamiSquare Koi Nami [S|L] - 50% off
SingedSquare Augmented Singed [S|L] - 50% off
SionSquare Lumberjack Sion [S|L] - 50% off
[4]
November 19
2013
November 26
2013
Flexible cost bundles:
1. The Bear Essentials bundle - 40% off, RP 2565 (RP 4242 with the champions):
VolibearSquare Runeguard Volibear [S|L]
SejuaniSquare Bear Cavalry Sejuani [S|L]
AnnieSquare Panda Annie [S|L]
TeemoSquare Panda Teemo [S|L]
2. Masters of Malpractice bundle - 30% off, RP 2047 (RP 3769 with the champions):
ShenSquare Surgeon Shen [S|L]
KennenSquare Kennen M. D. [S|L]
AkaliSquare Nurse Akali [S|L]
3. Biker Boys bundle - 50% off, RP 1982 (RP 3945 with the champions):
JaxSquare Vandal Jax [S|L]
TwitchSquare Vandal Twitch [S|L]
BrandSquare Vandal Brand [S|L]
VladimirSquare Vandal Vladimir [S|L]
GragasSquare Vandal Gragas [S|L]
4. Carry your carry bundle - 25% off, RP 3585:
ThreshSquare Thresh
ZyraSquare Zyra
NamiSquare Nami
LuluSquare Lulu
LeonaSquare Leona
[5]
November 22
2013
November 25
2013
NunuSquare Demolisher Nunu [S|L] - 50% off
ShenSquare Blood Moon Shen [S|L] - 50% off
ShacoSquare Royal Shaco [S|L] - 50% off
[6]
November 26
2013
November 29
2013
DravenSquare Soul Reaver Draven [S|L] - 50% off
DianaSquare Dark Valkyrie Diana [S|L] - 50% off
TalonSquare Renegade Talon [S|L] - 50% off
[7]
November 29
2013
December 2
2013
ViktorSquare Full Machine Viktor [S|L] - 50% off
LuxSquare Spellthief Lux [S|L] - 50% off
VayneSquare Aristocrat Vayne [S|L] - 50% off
[8]
December 3
2013
December 6
2013
TristanaSquare Guerilla Tristana [S|L] - 50% off
WukongSquare Volcanic Wukong [S|L] - 50% off
GarenSquare Commando Garen [S|L] - 50% off
[9]
December 6
2013
December 9
2013
ViSquare Neon Strike Vi [S|L] - 50% off
Lee SinSquare Acolyte Lee Sin [S|L] - 50% off
CassiopeiaSquare Desperada Cassiopeia [S|L] - 50% off
[10]
December 10
2013
December 13
2013
WarwickSquare Firefang Warwick [S|L] - 50% off
XerathSquare Scorched Earth Xerath [S|L] - 50% off
CorkiSquare Hot Rod Corki [S|L] - 50% off
[11]
December 13
2013
December 16
2013
SorakaSquare Divine Soraka [S|L] - 50% off
JaxSquare Temple Jax [S|L] - 50% off
Cho'GathSquare Loch Ness Cho'Gath [S|L] - 50% off
[12]
December 17
2013
December 20
2013
JannaSquare Frost Queen Janna [S|L] - 50% off
AnnieSquare Frostfire Annie [S|L] - 50% off
EzrealSquare Frosted Ezreal [S|L] - 50% off
[13]
December 20
2013
December 23
2013
KennenSquare Arctic Ops Kennen [S|L] - 50% off
FizzSquare Tundra Fizz [S|L] - 50% off
OlafSquare Glacial Olaf [S|L] - 50% off
[14]
December 24
2013
December 27
2013
RumbleSquare Rumble in the Jungle [S|L] - 50% off
JayceSquare Full Metal Jayce [S|L] - 50% off
RivenSquare Crimson Elite Riven [S|L] - 50% off
[15]
December 27
2013
December 30
2013
GragasSquare Gragas, Esq. [S|L] - 50% off
NunuSquare Grungy Nunu [S|L] - 50% off
ZileanSquare Groovy Zilean [S|L] - 50% off
[16]
December 31
2013
January 3
2014
KassadinSquare Harbinger Kassadin [S|L] - 50% off
MalzaharSquare Overlord Malzahar [S|L] - 50% off
MordekaiserSquare Infernal Mordekaiser [S|L] - 50% off
[17]
January 3
2014
January 6
2014
CassiopeiaSquare Mythic Cassiopeia [S|L] - 50% off
SionSquare Barbarian Sion [S|L] - 50% off
GangplankSquare Spooky Gangplank [S|L] - 50% off
[18]
January 7
2014
January 10
2014
TeemoSquare Panda Teemo [S|L] - 50% off
BlitzcrankSquare Piltover Customs Blitzcrank [S|L] - 50% off
BrandSquare Vandal Brand [S|L] - 50% off
[19]
January 10
2014
January 13
2014
CorkiSquare Urfrider Corki [S|L] - 50% off
RammusSquare Chrome Rammus [S|L] - 50% off
JaxSquare Vandal Jax [S|L] - 50% off
[20]

References

Skin Sales Super-Thread by Coreporeal