Yes, you can sniff traffic in a switched network. Are you trying to do this at home? If so, then it is very easy since you would probably be using one hub and one network. I have to sniff traffic at my office from time to time and it is a little more complicated since this is an enterprise level network with multiple vlans. If you told us how your network is constructed, we may be able to give you a better idea on how to do this.