That was last year, a bit out-dated, however I can put that in, aswell as the KERS from 2009. But I want something from this season so I don't look out-dated.
Not the introduction of a part but the removal of it...? The EBD ban allowed Ferrari to be a pace setter at Silverstone. Another non-recent example may be the outwash front wing endplates which allowed McLaren to make a large leap up the grid when they were intoduced at Germany '09. Or without the double diffuser in 2009 Brawn would probably have won a lot less.
It's quite hard relate it to 2011 as only Red Bull and McLaren were consistently winning, with Red Bull's success derived from the evolution of the 2009 spec aero rules, with McLaren perhaps you could talk about the 'L' shaped sidepods which allowed cleaner airflow to the rear of the car.