What options do I have if I paid $1500 in refundable deposits with a summer campground/resort however they now refuse to return my calls and refund my money?

First, you can sue them to get your money back--IF you have good grounds to recover it. While you say the deposit is refundable, make sure that you have complied with whatever requirements (e.g. how long to seek a refund) that may have existed; if you have, and they still won't return the money, then suing is the best way to get your money back.

Second, if you think they acted with criminal intent--for example, this was a scam, and they never intended to give people their money back or provide something of value--you could also report them to the authorities (e.g. the police). Note that since the authorities primarily act to apprehend and punish lawbreakers, not recover victim's money, this does not necessarily help you recover your deposit.