My ex-gf has a bad oil leak in her 99 Subaru wagon, not sure what model. She hasn't brought it over yet, but I'm wondering if there are common places for leaks to develop with these motors?

Headgasket, front oil pump, valve cover (normal on any car) and sometimes the oil pan. Keep in mind the drain plug requires a gasket that usually doesn't get replaced at every oil change like it should.