I think in most cases when the plane's condition has come to the point where it's about to crash then a parachute, although a cool idea, probably would be useless. TWA, Pan Am, Air India, Swissair, Iran Air, Egyptair, Alaska Air etc.. all happened so fast or the circumstances were so particular that a parachute would have been either useless or in Alaska's case maybe a greater hinderance to getting down safely.
Another alternative in a perfect world would be larger swept wings or blended wings that would allow a jet to more easily glide to earth.. or giant inflatable air bags on the outside to allow for a more controlled Mars-like landing that would hopefull keep the plane upright and passengers in one piece.. or if nothing else at least keep it afloat if in water. All this though would increase weight penalities, fuel consumption, reduce range and be prohibitively expensive... and this does nothing if the jet is on fire or breaking apart.
Another possibility is a giant inflatable helium filled balloon or those outside air bags I mentioned above.. but then where do you store that much helium on a 747 and would it inflate in time and would it be effective at -50 degrees??.. would do wonders for weight penalities though
I guess I'm really just waiting for the first anti-gravity device that might solve all these problems...