I figured I'd start this one here. So far I have found three excellent ones which are pretty easy:
1.) Wear sunglasses. Seriously, food looks a lot less appetizing when it is all dull and desaturated (you see less color when it is darker.) Indoor environments will make the latter more noticeable. Your rods do not see color ;)
2.) Eat 100% dark chocolate. It is bitter and suppresses my taste buds at least enough to be noticeable.
3.) Drink a non-flavored fiber mix in a cup of warm water. This will totally turn off your taste buds and kill any appetite you might have, or at least it does with my fiber mix. Bonus points for squirting a little bit of lemon juice/extract in with it. The sourness works well.
What do you guys and girls have to offer?
One of the ways I made junk food or processed food seem less appetizing was to look up the ingredients on the lable and their possible health problems before actually trying to put it in my mouth.
The things we think are disgusting (as in skin-crawling, not bleah, yucky) are culturally conditioned. Most westerners would blanch at the thought of eating a duck fetus, but it's a common snack in Vietnam. Likewise some rabbis will turn green at the thought of having accidentally ingested some shrimp. And most of us once thought of organ meats as, well, tripe.
This kind of conditioning comes from the people around you. If everyone you hang out with thinks fried grasshoppers are a great snack and partially hydrogenated palm oil is basically sewage, soon you will too. It's not practical (or friendly) to replace or recruit all your friends to your diet, but hanging out here and in other Paleo communities helps a lot.
Consider "enlightened tasting" a la Tim Beneke on Seth Roberts' board. Swirl the food around in your mouth, but don't swallow, you may lose your craving. http://boards.sethroberts.net/index.php?topic=5932.0
Todd Becker touched on this as well. http://gettingstronger.org/2010/04/overcoming-addictions/