Here are some of my favorites:
Homemade Trail Mix: Roasted peanuts (unsalted), raisins, sunflower seeds and pepitas (dried pumpkin seeds. Super high energy! Yes, it has a lot of fat, but they're the healthy kind of fat and your body needs fat. I buy all the ingredients at Trader Joe's (TJ's) and mix it on my own- they have really great prices on nuts and dried fruit.
Dried Unsweetened Mango: Right now I can only find these at TJ's, but they're amazing and inexpensive. They are also really filling. You'll eat a few pieces and think nothing of it, but ten minutes later be FULL.
Greek Yogurt: I buy tubs of 2% plain (cheaper than buying individual units) and then mix in fruit and a tiny bit of honey. Yum! Right now my favorite thing to mix in is pomegranate. Frozen fruit is easy and inexpensive- blueberries, peaches and strawberries :) Not only is this cheaper, but tastes wayyy better than premixed and sugar laden varieties. Greek yogurt is thicker than regular yogurt and has 2x the protein (keeps you full longer) and half the carbs.
Lara Bars: I've been hearing about these bars for awhile now, but they always sounded super healthy. So healthy that there was no way they could possibly taste good. Then I tried Peanut Butter and Jelly flavor. It was AMAZING. I couldn't believe how good it was. And the ingredients? Dates, peanuts, unsweetened cherries and sea salt. I have tried a couple other flavors and sadly I only like the PB&J so far, but I'll keep trying. These are a pricey $1.15 or so, but worth keeping a few stashed for snacking emergencies. Also- don't be concerned by the small size. These are 100% real food and full of energy, most of the typical bars at the grocery store have a lot of ingredients that increase the size of the bar, but won't do anything to fill you up.
Hummus: Homemade hummus with just about anything for dipping- carrots, pepper strips, snow peas, celery, pita, crackers...I could go on.
Almonds: I like raw and unsalted. (these are Brian's favorite)
Hard-boiled Eggs: Free-range and delicious. No mayonnaise needed.
And of course, apples, bananas, pears, berries, baby carrots, celery, and cucumber. Bananas are especially awesome because they are so naturally portable (and really high in potassium- great for runners).
I'm going to be traveling this week and will definitely be bringing my own snacks to the airport. Yay for saving money and being healthy!