How strong of magnetic field would noticibly attract a person?

Humans are weakly diamagnetic. Rather than being attracted by a magnetic field we would tend to repel the lines of force.

Look at the work of the High Field Magnet Laboratory http://www.ru.nl/HFML/, in particular http://www.ru.nl/hfml/research/levitation/diamagnetic/ where they demonstrate levitation of a living frog. It took about 16T to levitate the frog.