If you are not doing anything too crazy you can just change your ip to a different one provided you have a dynamic address from your provider. Get some software to change the MAC address of your network card. Unplug your modem, change your mac address, and plug your modem back in. Dynamic addresses are usually tied to the MAC address so when you change it and re-plugin your modem they will give you a different address because they see it as a different computer. Of coarse this only works if the computer that you changed the MAC on is connected directly to the modem.