Apple has started to offer a limited selection of refurbished iPad 2 units on its online store. Currently, the models offered include 32GB Wi-Fi + 3G models on AT&T and Verizon, 64GB Wi-Fi only models, and 64GB Wi-Fi + 3G models on both AT&T and Verizon. Each model is priced at $50 less than retail, making the prices for the three models mentioned above $679, $649, and $779, respectively. It is not clear how much stock Apple has, although…