Some people put pullup resistors on buss lines that operate in a 3-state manner to restore the level on the bus quite quickly after the completion of a cycle. Another reason for adding resistors is to lower the impedance of the address bus. In designs with CMOS chips that have extememly fast rise/fall times this decreased impedance can act as a termination on the buss lines. This termination can lower the amount of ringing on the lines.

Michael Karas