What you're seeing:
If a slinky is hung by one end such that its own weight extends it, and that slinky is then released, the lower end of the slinky will not fall or rise, but will remain briefly suspended in air as though levitating.
[T]he best thing is to think of the slinky as a system. When it is let [go], the center of mass certainly accelerates downward (like any falling object). However, at the same time, the slinky (spring) is compressing to its relaxed length. This means that top and bottom are accelerating towards the center of mass of the slinky at the same time the center of mass is accelerating downward.
(Hat tip: Kottke)