I have no idea what this is....ask Coley, he found it...I'm thinking it's about a mm in diameter and appeared to be segmented

It writhed energetically coiling and recoiling; these pictures were taken at intervals of about a second. I thew it back outside after photographing it; I hope it's not a dangerous intestinal parasite!

Amy figured out what it is: a horseshow worm. They have their own Phylum, Nematomorpha. The adults, like in the picture are free living, the larvae are parasitic on various invertebrates. They're also called Gordian worms; I regret now not posting the picture where it is coiled up in a tight knot!