A firewall will keep others from seeing your IP address, so you should be behind a router. If you are, outsiders cannot see your IP address.
What makes you think that there is a need to hide your IP Address when browsing the web? I usually hide mine when replying emails that contained sensitive information such as bank accounts, pins and etc. (I guess I am paranoid) I believe that prevention is better than nothing (or cure). We have many choices of software, right now I am currently using virtual private network hidemyass.com. We can also use proxy servers and etc.