I've got a website link for you.
This person has chronciled all the places in their house suitable for hiding things.
Behold, the visual:

So, if you're into any less than above-board activity and want to cover your tracks, or just want to hide items so well you can't find them again (cause, as a Mom, I'm really good at that)... consider using your tampon box, or hell.... just go dig a hole in the backyard as advised.
Seriously, I wish I had this much time on my hands.