The first question I'd ask is, are you sure it's an addiction?
The way addiction is usually defined is something that you can't stop that is harmful to you in some way or preventing you from carrying out your everyday functionality.
Domai is a great site - I personally go there once a day, just to keep the sight of nudity a common thing in my life. The great thing about the site is that it's not inherently sexual, it's simply nudes with a common theme.
In order to figure out why you might be addicted to pornography or sex - what are you beliefs about sex? Is what you're doing wrong? Do you think sex is wrong? It's odd, but some people start carrying out an action simply because they believe it's the wrong one, or they feel guilty for something. Porn and/or sex is not a bad thing for you unless it is causing harm. The bottom line: Is it causing harm? Is it taking you away from things you should be doing instead?
You might also try reading about naturism. It's astonishing how many people don't know about the concept. Most of the time people view porn not because of sex itself, but because of the visual stimulus presented, and much of the time - it's simple nudity in a sexual context. People build an assocation of nakedness with sex, but this association is distorted and unnecessary. While sexuality will always be a part of human nature, there is no need to obsess over it. Check out
Nudist - American Association for Nude Recreation, to start off with, for reading up on naturism. A lot of people have the experience of being disgusted and repulsed by porn after they've spent time for hours themselves in the nude, as well as seen lots of others nude - in a nonsexual context. It truly is an interesting, strange treatment, and from a conservative view, the exact opposite of what you might believe to be effective.
But why not give it a shot? Instead of looking at porn, start looking at non-sexual images of nudity for a while. If you're 'addicted' and you figure you're going to be looking at it for a long time anyway, just start shifting it to something different, but something where you're confronted with breaking your old association.