In a preliminary study on rodents, a combination of GABA -- the major inhibitory neurotransmitter in our central nervous system -- taken together with 5-HTP (an amino acid that converts in the brain to serotonin) improved sleep quantity and quality. The researchers say, "Combined GABA / 5-HTP may be effective in patients with insomnia by providing sufficient sleep." In my experience, I have not found GABA to be as effective as 5-HTP for sleep induction, but I have yet to try the combination. See more information about supplements and sleep.
