Do you have any paperwork from them for the deposit? Hopefully with a rough delivery date?

As a start, Id send them a letter, CC it to yourself. Inform them they have failed to deliver within reasonable time, and within their provided delivery time. Inform them they must return goods and deposit, as nothing has progressed. And inform that return must be made with 30 days, or you will prosecute in small claims court. Then be ready to take them to court. Especially with the time of year, they will probably throw your stuff and money back at you, since court stuff will cost them more in lost time.

Just a thought on how to deal with this. Sounds like they are either waiting on money, lost/screwed something up, or really dont like you for some reason!