Just how healthy are we talking? I don't find fruit or vegetables to be filling enough (well, an entire pack of grape tomatoes would be filling, but I think that that much tomato can be hard to digest). I don't currently have any snacks at my desk (and succumb to the snack vending machine instead), but things I have considered include nuts, granola bars, graham crackers, Triscuit, and beef jerky. I haven't ever bought it myself, but there is also tofu jerky, but I worry that there's too much sugar (and maybe sodium) in the seasoning of tofu jerky.