Blaine,
Part of I2C's features is 2 lines (SCL & SDA) creating a bus which can handle multiple slaves & masters.
Also, I know Phillips (as well as others certainly) makes a number of chips which enhance the protocal and extend the bus in many ways? Capacitance on the lines needs to be taken into account, but there are ways to deal with that too.
So, what are you trying to do that requires more than one bus? Do you really need it? It could save a few pins if you don't have to have a second bus.

Steve