Stumbled upon this word over the weekend, loving it:

hypnagogic: adj. 1. Inducing sleep; soporific. 2. Of, relating to, or occurring in the state of intermediate consciousness preceding sleep: hypnagogic hallucinations.

See also: Hypnagogia, hypnopompic.

I wouldn't call myself a word nerd by any means but I was pleased to know there was a name for the state between wake and sleep.