I have spent quite some time researching best ways to ship by to the USA. I haven't found a good option for sea-shipping, unfortunately. I have about 200-300 kilos and don't care how long it will take to get there as I am traveling for 6 months after I leave here.

Best options I have found are through the cargo rates on American and US Airways. I have been quoted around 850 CHF for 200 kilos, with an average of 3-5 days delivery (someone must pick it up at arrival airport within 3 days and cost does not include the customs fees). You have to drop it off about 2+ hours before you want it to be shipped. Because I have only been researching costs, I am not sure if you actually have to reserve space on an aircraft or not.