Unfortunately no such program exists though you could change your mac address. Even going through a proxy brings up it's own set of concerns because of the various ways websites query data through your web browser just simply going to a web-based proxy is not enough. Another alternative to that is called onion routing which involves mixing up the traffic within a group of people and have your data exit via someone elses connection. Here's some links for some onion routing and a proxy site.
Proxy -
Proxy.org - The Proxy Authority
Onion Routing (tor) -
Tor: anonymity online
Doing the standalone for tor takes some setup, if you have no idea what your doing then download this version of tor as it contains a version of firefox that is setup to use it. Even that is still not enough and the there is a bookmark within it that gives you some advice on fully securing.
http://www.torproject.org/torbrowser/dist/tor-browser-1.1.0_en-US.exe
Note*** - None of these are fully effective as tor exit nodes have been hacked and whats to stop leo from requesting the information from the proxy and then the proxy giving up your ip? Not a whole lot so there you have it.