My faves:

O'Connors, Rt 18 (Lake rd) in Porter. Good prices, nice plants, nice people AND three yellow labs!! If you're going to Zehrs do yourself a favor and stop here too. It's between Wilson and Youngstown.

Garden Sensations, http://gardensensations.net/nursery/ they have a .35 perennial sale in the spring!! I've only been there for that but they are super nice, and who can argue with .35 (per cell) perennials.

Heimillers, http://www.heimillergreenhouses.com/ again good prices and plants. Family run. Haven't been yet this year but I will be! Kind of off the beaten path but worth the trip.

Lavocats, http://www.lavocatsnursery.com/ Really great variety, good healthy plants, family run AND good prices.