Exactly which packs are not available (from FFG or most retailers)?

Thanks!

From what I can tell, the hardest ones to find in stock are:

Madness and Horror:
* Call of Cthulhu LCG: Mountains of Madness Asylum Pack
* Call of Cthulhu LCG: Ancient Horrors Asylum Pack

Summons of the Deep:
* Call of Cthulhu LCG: Spawn of the Sleeper Asylum pack
* Call of Cthulhu LCG: The Horror Beneath the Surface Asylum Pack
* Call of Cthulhu LCG: The Antediluvian Dream Asylum Pack

With that being said, you can probably obtain most of them by shopping at a variety of online stores and ebay. Or if you are lucky, your local store may have something.

I am actually new to this game (and the FFG forums), so there may be better advice out there, but I thought I would try to help.

Lots of Horror Beneath the Surface and Antediluvian Dreams at my FLGS. Only waiting for Spawn of the Sleeper to complete my collection now, but who knows when that reprint will be in stores?

You'd have to be very lucky to find any of the two standalone packs in any store now. If you do find them, buy as much as you can!