The most up-to-date information on the core of the Earth would probably be in journal articles. If you have a subscription (through a university, community college, etc) to a database like GeoRef or GeoScienceWorld, look through there. Otherwise, you can use Google Scholar and at least get to read a few abstracts.
Good luck! It would be easier to answer this question if you were a little more specific in what you were looking for.
