>> are all other 'passage tombs' aligned to happenings in the sky or do any have passages that don't line up with
>> anything in particular?

Well, those of Carrowkeel and around Sligo in general all point at Knocknarea or Carrowmore (depending on who you read).

There are several though that don't seem to point at anything. Seefin, Fourknocks, Carrowkeel cairn B and one other I can't think of point very north-ish. Unless there's a star based alignment I don't know what they would be aligned to, although some say that Fourknocks points at Newgrange (but you need a very thick marker pen on a small scale map to make the point valid :-)