These are glossosomatids, Jason. They are probably Glossosoma nigrior, though it is possible that we are looking at mixed species. The ones to the right with their aggregate of similar sized grains are classic Glossosoma, while the ones to the left with the large anchor pebbles could possibly be Agapetus. Regardless, they're all commonly referred to as saddle case makers.
The large caddisfly case (really less than 1/2 inch) is a Brachycentridae larva. The other cases are actually the protective sheaths of black fly (Simuliidae) pupae. The two antler-like pieces sticking out of each one are not legs, but antennal sheaths.
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Larva: Many classes of aquatic insects, such as caddisflies, midges, craneflies, dobsonflies, alderflies, and many more, are known as "larvae" rather than "nymphs" in their juvenile stages. They have mostly soft bodies rather than hard exoskeletons. These insects also advance through a "pupa" stage before reaching adulthood.
Pupae: Any insect which spends most of its juvenile lifetime as a larva first becomes a pupa for a time before emerging as a fully grown adult. Depending on the species, the pupal form can be very important for fly fishermen to imitate.