Pistachios make a great snack because not only are they lower in (albeit healthy) fat than other nuts, but they're also high in antioxidants and vitamin A. Also, having to shell each pistachio as you eat makes it a snack you can really savor instead of gobbling by the handful. That's why I've been so happy to discover these 100-calorie pistachio snack packs ($22 for 24) from Wonderful (yes, the company responsible for that creepy/funny Steven Colbert Super Bowl commercial).
The packs are perfect for throwing in my bag when I'm traveling or just on the go and don't have time to eat, and the amount in each pack is surprisingly satisfying. Of course, these prepackaged products aren't exactly as cheap or eco-friendly as buying in bulk and dividing into snack packs yourself (for reference, 100 calories is about 29 roasted and salted pistachios), but I've found them to be convenient alternatives to the vending machine or other unhealthy snack temptations.