Trabant, Wartburg, Moskvitch, Zastava, Lada, Skoda,... I guess all of them had a long waiting lists. I don't know if it was a joke but I've heard that people would leave their spots in last will and testimony to their kids.
Not sure about others but in the '80s nobody waited for Zastava. All over the country foreign cars were "assembled" (Opel, Renault, Citroen, WV Golf...) so while Zastava priduced cheaper cars they weren't the only game in the town and they kinda produced enough to satisfy demand (actually I believe that they would prefered that demand for their cars was even larger). Not sure about 60's and 70's though.