The cap on magic and gold find is 300%, but you there are ways to go above that!
Just a quick warning to people out there. In patch 1.0.4 MF and GF was capped at 300% before NV. With Nephalem Valor you could hit 375%.
However, currently followers and shrines don’t count towards the 300% limit, so with a full NV stack, you can achieve 405% MF/GF. This is pretty awesome, but it is not intended.
Currently the devs are looking in to fixing this small bug, so in the near future your followers will count towards the 300%. This also means, that you shouldn’t go out and spend stupid amounts of money on MF/GF gear for your followers, since you will hit the 300% cap pretty fast as you level up paragon levels fast in the beginning.