My best insomnia strain so far is Mephisto 24 Carat. I hear good things about Anvil though if you can get your mitts on some seeds, and it is more productive than 24C.
Next best was Northern Lights by Seedsman. None of the other stuff I have tried was in the same league for sleep. Before growing weed, I went through a lot of dispensary stuff searching for sleep meds, but never found anything as good as my home grown meds.