How to inexpensively move across country?

I'm currently living in Florida and want to move to Denver. I have family that lives in Denver that are going to let me stay at their house until I find my own place so that's all covered. I'm mainly wondering, how should I go about moving all of my stuff as cheaply as possible? I'm in my early twenties so I don't have a whole lot to move. I have a bedrooms worth of stuff that I have to move i.e. Bed, two night stands, computer desk, dresser, futon frame, and other nick nacks like four guitars(I will not part with any of my guitars) computer stuff, DVDs, games, etc. All I have is a little Ford Focus as a vehicle.

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