We signed a contract to purchase a new home and the builder is behind schedule on completion of the home and/or hasn't started construction, how do we get out of the contract or get our deposit back?

Read your sales contract very carefully.  You may have grounds for a breach of contract by the builder.    Builders put in estimation dates for delivery, however, if a firm home-completion date has been designated in your contract, your builder may be liable to you for damages.  You may wish to contact a local real estate attorney for further details.