you may also use a Microchip PIC-device with build-in SPI bus. The PIC has also enough free I/O-pins. So you can program an "intelligent" I/O-Expander .
if u just want to haver additional I/O-Lines at the SPI u can use devices like the 74HC595 on your SPI-Bus. They are extremely cheap and u don't have to put software in them to get them running.
Best regards,