Internet, what's your opinion on snack bars, aka power bars or cereal bars?
This article was a good find for me on breaking down the nutritional value on the labels. Clearly, you want something as nutritional as possible. In that realm, I like Fiber One bars by General Foods. (Then again if you're on a long bike ride, you might like something with more carb value.)
I remember a brand--back in the dark ages when I was in college--that was popular among me and my friends. Actually, the name of it escapes me but it was kind of crunchy and had a chocolate outer layer. Yum. (Was it Carnation? Does anyone recall?)
These days it probably wouldn't pass any of the low-fat, low-carb tests but man, it was tasty-licious.