Chief Exalted Officer

As I see it, best way will be to farm Zaxxis up in Netherstorm for their insignia's, and turn them in to Nether-Stalker Khay'ji at Area 52 for the quest Another Heap of Ethereals.

The drop rate is approximately 50 % for the insignia's.

Each turn-in of 10 Insignias grants +250 Consortium reputation.

The Zaxxis also have a chance to drop a Ethereum Prison Key.

Also, doing the daily dungeon quest (Non-heroic) rewards you with one Ethereum Prison Key, and +250 reputation with The Consortium, as well as +250 reputation with the instance's respectable faction. ( For example Sha'tar for any Tempest Keep instance. )

Just found a brilliant way to max out your rep with Consortium w/o all the farming. Simply clear up to Nexus-Prince Shaffer, engage him, but don't attack. He spawns Ethereal Beacons (8/9 rep per) every few seconds, allow them to spawn into Ethereal Apprentices (23 rep per)
I simply went afk for 5 mins, as a Prot War i took minimum damage, or just watch tv/youtube/facebook for a bit, tab back in, kill all Apprentices, repeat!
Fantastic way, currently doing it as i type this out.
(edit) After tracking 19000 to 21000, i was able to get 1000 rep every 10 minutes using this method w/o using [item=64402] this rep will be the same for anyone, as his spawning doesn't ever slow or stop, it's just a matter of a time sink.

Running heroic Mana Tombs (Auchindoun) gives reputation untill exalted. Easily done by a couple of level 80's. 1.5 to 2k reputation per run. Average run takes - depending on group - 30minutes.