I keep a couple of 'filling' snacks around - just in case. Ie. piece of fruit, small serving of nuts, package of oatmeal, kashi granola bars, or in-case-of-emergency-break-glass kind of snack...
POPCORN. It really does help, and takes a while to eat a small amount - so I get that full feeling over a period of time, rather than immediately.
When I find myself just out of control hungry, I usually need a little more fat. I go for something dense, sweet and containing fat and fiber, like peanut butter on sliced apple. It is a few hundred calories, but it's healthy and it almost always quells the munchies.
I have noticed for some reason there are days that I am just hungry. Not like a mental thing but truly physically hungry. I have found not letting myself get too hungry to start with is a big key, but sometimes even that doesn't seem to help.
So, please share. When you are HUNGRY what do you eat that is satisfying but doesn't blow your day?