The list is ordered from the oldest to the most recent announcement made by the Riot Games Inc. 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 Season Eight
Early Sales


Period Sales Link
December 15
2009
December 15
2009
Ashe FreljordCircle Freljord Ashe [S|L] - 50% off [1]
January 16
2010
January 16
2010
Blitzcrank RustyCircle Rusty Blitzcrank [S|L] - 25% off, removed from the store soon after. [2]
January 18
2010
January 20
2010
Master Yi AssassinCircle Assassin Master Yi [S|L] - 50% off [3]
January 21
2010
January 21
2010
Nunu SasquatchCircle Sasquatch Nunu [S|L] - 25% off [4]
January 22
2010
January 24
2010
Twitch KingpinCircle Kingpin Twitch [S|L] - 50% off [5]
January 29
2010
January 31
2010
Dr. Mundo ToxicCircle Toxic Dr. Mundo [S|L] - 50% off [6]
February 6
2010
February 9
2010
Evelynn ShadowCircle Shadow Evelynn [S|L] - 50% off
Ashe FreljordCircle Freljord Ashe [S|L] - 50% off
[7]
February 23
2010
February 25
2010
Nunu SasquatchCircle Sasquatch Nunu [S|L] - 50% off [8]
February 26
2010
February 28
2010
Teemo BadgerCircle Badger Teemo [S|L] - 50% off [9]
March 1
2010
March 3
2010
Cho'Gath NightmareCircle Nightmare Cho'Gath [S|L] - 25% off [10]
March 8
2010
March 10
2010
Amumu PharaohCircle Pharaoh Amumu [S|L] - 50% off [11]
March 12
2010
March 14
2010
Master Yi AssassinCircle Assassin Master Yi [S|L] - 25% off
Taric EmeraldCircle Emerald Taric [S|L] - 50% off
[12]
March 19
2010
March 21
2010
Malphite ShamrockCircle Shamrock Malphite [S|L] - 25% off [13]
March 19
2010
March 21
2010
Alistar GoldenCircle Golden Alistar [S|L] - 50% off
Poppy NoxusCircle Noxus Poppy [S|L] - 50% off
Twitch KingpinCircle Kingpin Twitch [S|L] - 50% off
[14]
March 26
2010
March 30
2010
Katarina MercenaryCircle Mercenary Katarina [S|L] - 50% off
Ashe FreljordCircle Freljord Ashe [S|L] - 25% off
[15]
March 31
2010
April 2
2010
Dr. Mundo ToxicCircle Toxic Dr. Mundo [S|L] - 25% off
Karthus PhantomCircle Phantom Karthus [S|L] - 25% off
[16]
April 1
2010
April 16
2010
Happy Urf Day Event
Warwick UrftheManateeCircle Urf the Manatee Warwick [S|L] - 99% off (first week)
Warwick UrftheManateeCircle Urf the Manatee Warwick [S|L] - 90% off (second week)
[17]
April 5
2010
April 6
2010
Cho'Gath NightmareCircle Nightmare Cho'Gath [S|L] - 25% off
Nunu SasquatchCircle Sasquatch Nunu [S|L] - 25% off
[18]
April 9
2010
April 11
2010
Pantheon RuthlessCircle Ruthless Pantheon [S|L] - 40% off
Taric ArmoroftheFifthAgeCircle Armor of the Fifth Age Taric [S|L] - 40% off
[19]
April 12
2010
April 16
2010
Veigar WhiteMageCircle White Mage Veigar [S|L] - 25% off
Pantheon MyrmidonCircle Myrmidon Pantheon [S|L] - 50% off
Teemo BadgerCircle Badger Teemo [S|L] - 50% off
[20]
April 17
2010
April 20
2010
Mordekaiser DragonKnightCircle Dragon Knight Mordekaiser [S|L] - 25% off
Master Yi AssassinCircle Assassin Master Yi [S|L] - 25% off
[21]
April 21
2010
April 23
2010
Teemo ReconCircle Recon Teemo [S|L] - 50% off
Taric EmeraldCircle Emerald Taric [S|L] - 50% off
[22]
April 24
2010
April 26
2010
Evelynn ShadowCircle Shadow Evelynn [S|L] - 50% off [23]
April 27
2010
April 30
2010
Corki RedBaronCircle Red Baron Corki [S|L] - 30% off [24]
April 30
2010
May 2
2010
Warwick BigBadCircle Big Bad Warwick [S|L] - 30% off
Annie RedRidingCircle Red Riding Annie [S|L] - 30% off
[25]
April 30
2010
May 3
2010
Mordekaiser InfernalCircle Infernal Mordekaiser [S|L] - 50% off
Jax VandalCircle Vandal Jax [S|L] - 50% off
Katarina MercenaryCircle Mercenary Katarina [S|L] - 50% off
[26]
May 4
2010
May 7
2010
Gragas ScubaCircle Scuba Gragas [S|L] - 30% off [27]
May 14
2010
May 16
2010
Tryndamere HighlandCircle Highland Tryndamere [S|L] - 50% off
Ezreal NottinghamCircle Nottingham Ezreal [S|L] - 50% off
Karthus PhantomCircle Phantom Karthus [S|L] - 50% off
[28]
May 25
2010
May 28
2010
Ashe SherwoodForestCircle Sherwood Forest Ashe [S|L] - 50% off
Gangplank SpookyCircle Spooky Gangplank [S|L] - 50% off
Mordekaiser DragonKnightCircle Dragon Knight Mordekaiser [S|L] - 50% off
[29]
May 28
2010
May 30
2010
Pantheon RuthlessCircle Ruthless Pantheon [S|L] - 65% off
Ashe FreljordCircle Freljord Ashe [S|L] - 65% off
Cho'Gath NightmareCircle Nightmare Cho'Gath [S|L] - 65% off
[30]
June 1
2010
June 7
2010
Morgana ExiledCircle Exiled Morgana [S|L] - 30% off
Sion HextechCircle Hextech Sion [S|L] - 30% off
[31]
June 4
2010
June 7
2010
Tristana FirefighterCircle Firefighter Tristana [S|L] - 30% off
Master Yi ChosenCircle Chosen Master Yi [S|L] - 30% off
Soraka DryadCircle Dryad Soraka [S|L] - 30% off
[32]
June 9
2010
June 11
2010
Nunu SasquatchCircle Sasquatch Nunu [S|L] - 70% off [33]
June 11
2010
June 14
2010
Kennen SwampMasterCircle Swamp Master Kennen [S|L] - 50% off
Dr. Mundo ToxicCircle Toxic Dr. Mundo [S|L] - 50% off
Amumu PharaohCircle Pharaoh Amumu [S|L] - 50% off
[34]
June 15
2010
June 18
2010
Taric ArmoroftheFifthAgeCircle Armor of the Fifth Age Taric [S|L] - 50% off
Teemo BadgerCircle Badger Teemo [S|L] - 50% off
Evelynn ShadowCircle Shadow Evelynn [S|L] - 50% off
[35]
June 18
2010
June 21
2010
Veigar WhiteMageCircle White Mage Veigar [S|L] - 50% off
Pantheon MyrmidonCircle Myrmidon Pantheon [S|L] - 50% off
Garen DesertTrooperCircle Desert Trooper Garen [S|L] - 50% off
[36]
June 25
2010
June 28
2010
Fiddlesticks SpectralCircle Spectral Fiddlesticks [S|L] - 50% off
Akali CrimsonCircle Crimson Akali [S|L] - 50% off
Sivir WarriorPrincessCircle Warrior Princess Sivir [S|L] - 50% off
[37]
June 28
2010
July 2
2010
Katarina RedCardCircle Red Card Katarina [S|L] - 30% off
Akali All-StarCircle All-Star Akali [S|L] - 30% off
[38]
July 2
2010
July 5
2010
Alistar MatadorCircle Matador Alistar [S|L] - 50% off
Anivia BirdofPreyCircle Bird of Prey Anivia [S|L] - 50% off
Taric EmeraldCircle Emerald Taric [S|L] - 50% off
[39]
July 6
2010
July 9
2010
Malphite ShamrockCircle Shamrock Malphite [S|L] - 50% off
Katarina MercenaryCircle Mercenary Katarina [S|L] - 50% off
Master Yi AssassinCircle Assassin Master Yi [S|L] - 50% off
[40]
July 9
2010
July 12
2010
Rammus ChromeCircle Chrome Rammus [S|L] - 50% off
Teemo ReconCircle Recon Teemo [S|L] - 50% off
Jax VandalCircle Vandal Jax [S|L] - 50% off
[41]

References

Skin Sales Super-Thread by Coreporeal