The preliminary reccomendations following the loss of the shuttle Columbia have been published at the official accident investigation site (see links). Tragically, it seems that complacency may be creeping back in at NASA: one possible cause, falling foam, has affected many previous flights.There are two basic changes recommended by the CAIB, namely that Shuttle Imaging on Orbit be a standard feature (bearing in mind that the US government have this ability, and that it’s rarely used). This facility is intended to be able to assess the condition of the orbiter after ascent.
Secondly that the examination of Reinforced Carbon-Carbon (RCC) components be made a comprehensive one to include all possible forms of non-destructive testing. This is in response to the most likely reason for the loss of the orbiter: that of failure of a structural RCC component in the leading edge of the left wing.
There is as yet no final verdict on the root cause of the RCC component failure: Much speculation exists with present favorite being either pre-existing damage not spotted by inspection or a strike from other material (foam from the tank for example).
The leading edge components are extremely complex and have many layers and treatments. If the thermal protection the RCC parts provide is breached, even in a small way, a super heated air stream can enter the wing and burn the structural aluminium components.