Magnesium. Magnesium (which resources can be severely drained by chronic alcohol abuse) deficiency can cause/exacerbate a number of conditions, including insomnia. I've been taking magnesium citrate and using a topical magnesium/Dead sea salt spray and I have been thrilled with the results. I was an insomniac before I was a drinker, so sleep is a precious commodity to me.
Actually, the topical spray is supposed to help with stress relief. Maybe it's a sugar pill effect, but I used it in the evenings during the early recovery jitters and found it very soothing.