In a BBC News report, “Costa Concordia cruise ship captain ‘went off course'”, this map is presented.
It’s credited to the shipping newsletter Lloyd’s List, which on its web site further credits the detail to data from AIS. Here’s a few trackers that keep measure of ship locations from AIS, the Automatic Identification System:
More detail on AIS from the US Coast Guard, and from the ever-handy Wikipedia.
This animation is credited to data from Vessel Finder.
You can find calculated tracks on marine charts that received datas from AIS;