[avmich]

Some experiments were done in early 2000 with inflatable aerobrake. The concept was shown to work, but experiments weren't a complete success. However this technology I'm sure can be applied to the task of returning the second stage.

https://en.wikipedia.org/wiki/Atmospheric_entry#Inflatable_h...

[raducu]

Or even more futuristic, plasma parachute/heat shield: http://www.nasa.gov/offices/oct/early_stage_innovation/niac/...