You can pick up an inexpensive 'Managed' switch to mirror (or SPAN) traffic from one or more ports to a different port. This should take care of your needs if you are only trying to analyze your Internet traffic. If you're doing LAN and or LAN and Internet and the traffic approaches the full 1Gbps you'll probably going to need a more powerful switch to see all the traffic.
I picked this one some time back for about $15 on sale (now $25):