I always have:
grape tomatoes
baby carrots
hummus
whatever fruit(s) look good and are priced well

Fruits! I always have strawberries, cantaloupe or an apple. Low calories and filling. And I love vegetables, so I keep PictSweet single serving veggies in my freezer at work.

I don't usually keep snacks "On hand" per say... I plan out my meals and pack them in a cooler to take to work or wherever with me.

I do have some things that I keep at home that can be tossed in my purse if I know I'll be out running errands somewhere that isn't appropriate to take my cooler with me, or if I am heading off to the airport. (Though I have taken my own food into eateries before!)

- Good quality protein bars - right now I like Quest Protein Bars, but Supreme Protein bars and Think Thin meal replacement bars are good too.
- Light string cheese/mini baby bell cheese
- Baby Carrots
- Almonds
- Apples
- Pouches of tuna
- Jerkey

Unless I chose to pack a protein bar, I will pack up a couple of things so that I have a good balance of macronutrients, e.g. Tuna and almonds with carrots, mini baby bell cheese and an apple, etc.