A few weeks ago, Warframe had its 2 Year Anniversary (of Open Beta). I myself have played for about 22 months, and looking back, I'm quite amazed with all the change that has happened, and what better way to celebrate change then making a list of all the (major) changes that have happened.
I'm going to start this with a basic outline, as I can't finish everything at the time of writing this.
Update 7, March 18th, 2013 (Correct me if I'm wrong, on any date.)
Open Beta Begins
New color palettes
Update 7.4, March 27th, 2013
Sentinel Weapons can now use mods
Update 7.5, March 28th (Easter Update)
New Destructable Crates
New Enemy Headgear
Brokk Skin is added
Update 7.7.3, April 1st, 2013
New levels added to Grineer Asteroid and Corpus Outpost tile sets
New animations for Infested enemies
New Grineer helmets for Trooper, Seeker and Commander
Update 7.8, April 19th, 2013
Added up/down arrows to objectives on the minimap if objective is above or below the player's current level
Update 7.9, April 26th, 2013
Added new damage deformers for enemies, meaning more ways to dismember your foes.