Digital Rumination: 2014

DROPS - 23
ACHIEVEMENTS - 12

Vanilla/Classic - Lvl 60 - (4)

Ahn'Qiraj (4)

The resonating crystal mounts can drop from most of the trash in the 40 man AQ raid instance, located in the south of Silithus. Unfortunately they can only be used inside the instance but do count to your total:

http://www.wowhead.com/item=21218 - DROP - 14%

http://www.wowhead.com/item=21323 - DROP - 14%

http://www.wowhead.com/item=21324 - DROP - 14%

http://www.wowhead.com/item=21321 - DROP - 1.2%

The http://www.wowhead.com/item=21176 is no longer obtainable and was originally obtained by ringing the Scarab Gong within 10 hours of the first person to ring it on your server.
It is also the only legendary mount within the game.

The Burning Crusade - Lvl 70 - (2)

Karazhan (1)

http://www.wowhead.com/item=30480 - DROP - Attumen the Huntsman - 0.85%

Tempest Keep (1)

http://www.wowhead.com/item=32458 - DROP - Kael'Thas - 2%

Wrath of the Lich King - Lvl 80 - (12)

Eye of Eternity (2)

These mounts were originally assigned to either 10 or 25, however they can now drop from both difficulties:

http://www.wowhead.com/item=43952 - DROP - Malygos - 3%
http://www.wowhead.com/item=43953 - DROP - Malygos - 4%

Icecrown Citadel (3)

http://www.wowhead.com/item=50818 - DROP - The Lich King Heroic - 1%
http://www.wowhead.com/item=51954 - ACHIEVEMENT - http://www.wowhead.com/achievement=4602
http://www.wowhead.com/item=51955 - ACHIEVEMENT - http://www.wowhead.com/achievement=4603

Obsidian Sanctum (2)

To enable these mounts to drop, you must leave all 3 mini boss drakes alive before attacking Sartharion. They do not drop if this pre-requisite is not met.

Cataclysm - Lvl 85 - (10)

General (2)

Requires contributions from Blackwing Descent, Bastion of Twilight and Throne of the Four Winds:
http://www.wowhead.com/item=62901 - ACHIEVEMENT - http://www.wowhead.com/achievement=4853

Requires 8/10 or 20/25 guild group to gain the achievement, requires exalted with guild to purchase (does not require participation in achievement):
http://www.wowhead.com/item=63125 - http://www.wowhead.com/achievement=4988

Dragon Soul (4)

http://www.wowhead.com/item=78919 - DROP - Ultraxion - 1%
http://www.wowhead.com/item=77067 - DROP - Deathwing - 4%
http://www.wowhead.com/item=77069 - DROP - Deathwing Heroic - 2%
http://www.wowhead.com/item=77068 - ACHIEVEMENT - http://www.wowhead.com/achievement=6169

Firelands (3)

http://www.wowhead.com/item=71665 - DROP - Alysrazor - 2%
http://www.wowhead.com/item=69224 - DROP - Ragnaros - 1.3%

http://www.wowhead.com/item=69230 - ACHIEVEMENT - http://www.wowhead.com/achievement=5828

Throne of the Four Winds (1)

http://www.wowhead.com/item=63041 - DROP - Al'Akir- 1.5%

Mists of Pandaria - Lvl 90 - (7)

General (2)
Requires contributions from Mogu'shan Vaults, Heart of Fear and Terrace of Endless Spring:
http://www.wowhead.com/item=87773 - ACHIEVEMENT - http://www.wowhead.com/achievement=6932

Requires 8/10 or 20/25 guild group to gain the achievement, requires exalted with guild to purchase (does not require participation in achievement):
http://www.wowhead.com/item=85666 - http://www.wowhead.com/achievement=6682

Mogu'shan Vaults (1)

http://www.wowhead.com/item=87777 - DROP - Elegon- 1.3%

Throne of Thunder (3)

http://www.wowhead.com/item=93666 - DROP - Horridon- 1.6%
http://www.wowhead.com/item=95059 - DROP - Ji-Kun- 1.9%
http://www.wowhead.com/item=93662 - ACHIEVEMENT - http://www.wowhead.com/achievement=8124

Siege of Orgrimmar (1)

http://www.wowhead.com/item=104208 - ACHIEVEMENT - http://www.wowhead.com/achievement=8454