I empathize! I work from home most days of the week, and my desk is in my kitchen, so I spend most of my time about two steps from snacks, and more often than not, I give in to them. A few stragegies I've treid that seem to help:
Floss! I am pretty maniacal about oral hygine, so if I'm terribly tempted to eat, I'll go brush my teeth really thoroughly and floss and then gargle with some Listerine. I'm less likely to eat because I don't want to undo my cleaning, and the after-taste of Listerine makes everyting taste yucky for a while anyway.
I make it okay to snack all I want on certain things, like raw veggies. I cut up a bunch of broccoli and cucumbers and stick them front-and-center in the fridge, and give myself permission to eat all I want of them. It usually satifies the have-to-eat urge, and actually helps me get my veggies in for the day when I other wise might skip them.
Tea! I invested in a huge variety of different Celestial Seasonings teas, and I try to drink them instead of eating when I know I'm not really hungry. I have enough variety of flavors that i really does seem like a snack when I'm drinking, say, the gingerbread cookie flavor. Yum.
Walk away: when I hit that afternoon slump and find I just can't think about anything but food, I grab my laptop and plant myself in a room far from the kitchen, and busy myself with something I can't easily leave. I find that simply not entering the kitchen for a while takes the whole idea of snacking away.
Porno! I know, this sounds weird, but bear with me. I find that the one thing I find absolutely incompatible with eating is sex. So if I want to erase any thoughts of nachos from my mind, I hop onto literotica a read a story of an "adult" nature. For hours afterwards, the very thought of cramming chips in my mouth is just gross. And it also reminds me that our bodies can give us pleasure in many more ways than just the sensation of taste.