Trebor Jung wrote:
Is the phoneme /c/ (palatal stop) that 'hard /j/-sound' that I've heard is found in Latin American (Castilian?) Spanish, spelled as <ll>?
RM:  No. IPA [c] to me is a peculiar beast-- it's a voiceless stop, basically a k but with the central part of the tongue contacting quite far forward on the hard palate. Rather like the k of Engish "key".  If you can hear any of the IPA websites, it seems in some cases to have a bit of a y-like release, similar to but not as noticeable as in English "cute".  There is a voiced counterpart, IPA "j with a crossbar", roughly like English g in "geese".  Personally I suspect these occur mainly as allophones of phonemic /k/ before front vowels, but if there are languages where the two are distinctive, I'm sure someone will tell us.
Spanish <ll> in most of South America is pronounced like English y (IPA j), in some areas with a little more friction, XSAMPA "j\" I think, and mainly in Argentina as a palatal fricative like French j, that is, XSAMPA "Z".  Castilian <ll> is of course a true palatalized [l] similar to English "million".