74hc595 for instance.
They are rather cheap.
Depending on what you are goint to control you might need other tuff as well. Like the Arduino pins you can't draw much current from the shift register pins.
Shift registers with high current draw capability are available but they are much more expencieve. You should alo conider your power upply needs.
If you tell a little about what you are going to control we could probably give better advice 