What is the cheapest way to cross the ocean? (Pacific and/or Atlantic)?

Im trying to start planning a bike tour around the world, but of course bicycle travel isnt possible in all areas. Im trying to use as little money as possible, does anyone know a cheapest way to get from north america to europe/asia? I know it probably sounds like a dumb question! But please help, thank you! (ie is there some kind of ship that goes from alaska to siberia?)

Freight ships take passengers occassionally. I met a chick in SE Asia who was travelling around the world entirely by surface transport - no planes! She took a Russian freighter from LA to Australia. She has a website. maybe send her an email for ideas.