My little sister's name is Charley and it's adorable. I love this name for a girl or a boy. I also know a little boy named Charlie. If you're naming a boy Charlie, use c-h-a-r-l-i-e but if you're naming a girl Charley use c-h-a-r-l-e-y. The y makes it more feminine, I think. Again, love this name for either gender!
In the US this name is heavily stereotyped as a "British boy name," at least where I live. It's pretty uncommon in the States, I don't know of a single Charley. Whenever me or one of my friends hears it, we automatically think "European lad." Funny how it can be so overused in one place but pretty rare in another.