You do not want a ‘hub’. It woud only cause your traffic to slow down when using more than one computer on your network.
Yes, you can plug the modem into a switch. Most of the switches that you woud purchase on the consumer side may be ‘smart’ switches, which means that there won’t be an assigned uplink port on the switch…it will figure out which port you have plugged the modem into. Any computers you plug into that switch should pick up an IP address from the modem. Another issue here is security. At the very least in this scenario you should be running antivirus and firewall software on your computer. Also, DO NOT routinely go on the Internet with elevated (administrator level) privileges. Windows XP and below do this by default…not good at all and you will definitely have problems not too long after being on the Internet.
A router would be the best solution, and will usually come with built in switch ports as well…allowing you to plug more than one computer into that router. It can help mask you from the Internet and use a private IP address (most likely 192.168.1.x) on your internal network..while connecting you to the public network.
Many consumer side routers, such as the Linksys Wireless routers, have those additional switch ports which allow you to plug directly into the wire, or go wireless as well should the need arise. Be careful if you decide to go wireless…you will want to set security on it…that’s another topic (so now back to your original question…).
Bottom line…either a switch or a router will work for you.