I know how to set a custom ringtone for a given caller on my phone: pull up the person's entry under People, open the menu and select "Set ringtone." However, this only applies to regular voice phone calls.
Is there a way to do a similar thing for the sound that plays when a "text" — by which I mean either SMS or MMS — is received? If so, what is it? The Messaging app's settings only seem to let me choose a single notification sound, but I'm hoping there's something I'm overlooking.