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 11
2016
November 14
2016
GalioSquare Enchanted Galio [S|L] - 50% off
NunuSquare Grungy Nunu [S|L] - 50% off
GnarSquare Dino Gnar [S|L] - 50% off
QuinnSquare Phoenix Quinn [S|L] - 50% off
[1]
November 15
2016
November 18
2016
LuxSquare Sorceress Lux [S|L] - 50% off
OlafSquare Marauder Olaf [S|L] - 50% off
VarusSquare Blight Crystal Varus [S|L] - 50% off
Kha'ZixSquare Mecha Kha'Zix [S|L] - 50% off
[2]
November 18
2016
November 21
2016
ShacoSquare Royal Shaco [S|L] - 50% off
KarthusSquare Pentakill Karthus [S|L] - 50% off
ZacSquare Special Weapon Zac [S|L] - 50% off
SionSquare Warmonger Sion [S|L] - 50% off
[3]
November 22
2016
November 25
2016
SorakaSquare Dryad Soraka [S|L] - 50% off
SejuaniSquare Darkrider Sejuani [S|L] - 50% off
JayceSquare Debonair Jayce [S|L] - 50% off
DravenSquare Soul Reaver Draven [S|L] - 50% off
[4]
November 23
2016
November 30
2016
Flash & Dash Bundle - 50% off - RP 3187 (RP 5389 with champions)

Stranger Danger Bundle - 50% off - RP 2811 (RP 5013 with champions)

Otherworldly Bundle - 50% off - RP 2999 (RP 5147 with champions)

Scrappy Duelists Bundle - 50% off - RP 2623 (RP 4482 with champions)

[5]
November 25
2016
November 28
2016
AniviaSquare Bird of Prey Anivia [S|L] - 50% off
VeigarSquare Veigar Greybeard [S|L] - 50% off
GravesSquare Mafia Graves [S|L] - 50% off
LissandraSquare Bloodstone Lissandra [S|L] - 50% off
[6]
November 28
2016
November 28
2016
VarusSquare Dark Star Varus [S|L] - 28% off
GnarSquare El León Gnar [S|L] - 31% off
KayleSquare Iron Inquisitor Kayle [S|L] - 31% off
TaricSquare Pool Party Taric [S|L] - 28% off
FizzSquare Super Galaxy Fizz [S|L] - 28% off
KindredSquare Super Galaxy Kindred [S|L] - 28% off
[7]
November 29
2016
December 2
2016
Kog'MawSquare Monarch Kog'Maw [S|L] - 50% off
JaxSquare Warden Jax [S|L] - 50% off
TeemoSquare Cottontail Teemo [S|L] - 50% off
FioraSquare PROJECT: Fiora [S|L] - 50% off
[8]
December 2
2016
December 5
2016
EvelynnSquare Tango Evelynn [S|L] - 50% off
ShyvanaSquare Ironscale Shyvana [S|L] - 50% off
AnnieSquare Frostfire Annie [S|L] - 50% off
AhriSquare Popstar Ahri [S|L] - 50% off
[9]
December 6
2016
December 9
2016
OriannaSquare Sewn Chaos Orianna [S|L] - 50% off
VolibearSquare Runeguard Volibear [S|L] - 50% off
RengarSquare Night Hunter Rengar [S|L] - 50% off
LucianSquare PROJECT: Lucian [S|L] - 50% off
[10]
December 6
2016
December 14
2016
Team Fire Mega Bundle - 50% off - RP 7570 (RP 13164 with champions)

Team Ice Mega Bundle - 50% off - RP 6345 (RP 10724 with champions)

[11]
December 6
2016
December 13
2016
Two rune pages for the price of one (IP and RP)
All boosts - 50% off
Summoner name change - 50% off

2017 Top Starter Bundle - 25% off - RP 2906

2017 Mid Starter Bundle - 25% off - RP 2906

2017 ADC Starter Bundle - 25% off - RP 2977

2017 Support Starter Bundle - 25% off - RP 3223

2017 Jungle Starter Bundle - 25% off - RP 3306

Siege and Poke Bundle - 50% off - RP 3375 (RP 5575 with champions)

Disrupt and Tank Bundle - 50% off - RP 2472 (RP 4113 with champions)

Style and Outplay Bundle - 50% off - RP 2811 (RP 5105 with champions)

Pick and Assassinate Bundle - 50% off - RP 2811 (RP 4867 with champions)

Stack and Scale Bundle - 50% off - RP 2172 (RP 4022 with champions)

Zone and Control Bundle - 50% off - RP 2511 (RP 4760 with champions)

Tilt Enemy or...Feed Bundle - 50% off - RP 2284 (RP 3718 with champions)

[12]
December 9
2016
December 12
2016
MaokaiSquare Totemic Maokai [S|L] - 50% off
NautilusSquare Warden Nautilus [S|L] - 50% off
DariusSquare Bioforge Darius [S|L] - 50% off
ZyraSquare Wildfire Zyra [S|L] - 50% off
[13]
December 13
2016
December 16
2016
NidaleeSquare French Maid Nidalee [S|L] - 50% off
AlistarSquare Marauder Alistar [S|L] - 50% off
GnarSquare Gentleman Gnar [S|L] - 50% off
ViSquare Demon Vi [S|L] - 50% off
[14]
December 16
2016
December 19
2016
GragasSquare Hillbilly Gragas [S|L] - 50% off
TrundleSquare Junkyard Trundle [S|L] - 50% off
YasuoSquare High Noon Yasuo [S|L] - 50% off
WarwickSquare Firefang Warwick [S|L] - 50% off
[15]
December 20
2016
December 23
2016
PoppySquare Battle Regalia Poppy [S|L] - 50% off
NunuSquare Demolisher Nunu [S|L] - 50% off
JinxSquare Mafia Jinx [S|L] - 50% off
BlitzcrankSquare iBlitzcrank [S|L] - 50% off
[16]
December 23
2016
December 26
2016
EzrealSquare Frosted Ezreal [S|L] - 50% off
Jarvan IVSquare Dragonslayer Jarvan IV [S|L] - 50% off
Tahm KenchSquare Master Chef Tahm Kench [S|L] - 50% off
TryndamereSquare Sultan Tryndamere [S|L] - 50% off
[17]
December 23
2016
December 26
2016
CorkiSquare Arcade Corki [S|L] - 28% off
ThreshSquare Dark Star Thresh [S|L] - 26% off
NamiSquare Deep Sea Nami [S|L] - 28% off
Dr. MundoSquare El Macho Mundo [S|L] - 28% off
Miss FortuneSquare Pool Party Miss Fortune [S|L] - 28% off
KledSquare Sir Kled [S|L] - 31% off
Miss FortuneSquare Arcade Miss Fortune [S|L]
Chromaskins Chromas: Amethyst, Aquamarine, Citrine, Peridot, Ruby - 33% off
TeemoSquare Cottontail Teemo [S|L]
Chromaskins Chromas: Amethyst, Aquamarine, Rose Quartz, Speckled, Turquoise - 33% off
[18]
December 27
2016
December 30
2016
MalzaharSquare Djinn Malzahar [S|L] - 50% off
BrandSquare Apocalyptic Brand [S|L] - 50% off
ZedSquare Shockblade Zed [S|L] - 50% off
HecarimSquare Elderwood Hecarim [S|L] - 50% off
[19]
December 30
2016
January 2
2017
SkarnerSquare Earthrune Skarner [S|L] - 50% off
GarenSquare Rugged Garen [S|L] - 50% off
AatroxSquare Justicar Aatrox [S|L] - 50% off
NamiSquare Koi Nami [S|L] - 50% off
[20]
January 3
2017
January 6
2017
GravesSquare Hired Gun Graves [S|L] - 50% off
RivenSquare Redeemed Riven [S|L] - 50% off
TalonSquare Dragonblade Talon [S|L] - 50% off
UrgotSquare Battlecast Urgot [S|L] - 50% off
[21]
January 6
2017
January 9
2017
SionSquare Lumberjack Sion [S|L] - 50% off
SorakaSquare Order of the Banana Soraka [S|L] - 50% off
UdyrSquare Definitely Not Udyr [S|L] - 50% off
SkarnerSquare Sandscourge Skarner [S|L] - 50% off
[22]
January 10
2017
January 13
2017
TristanaSquare Buccaneer Tristana [S|L] - 50% off
SivirSquare Bandit Sivir [S|L] - 50% off
VayneSquare Dragonslayer Vayne [S|L] - 50% off
IllaoiSquare Void Bringer Illaoi [S|L] - 50% off
[23]

References

LoL's Official Sales page