Hello Threadless people

I am embarking on a round the world tour next year

I would like to start off in San Fransisco, head up north to Seattle/Vancouver then cross over the Chicago and finally hit New York (then I fly to London)

can anyone tell me general flight costs?

or at least where to look?

also accomodation suggestions? I am going relatively budget on this leg of the tour

thanks in advance

globetrotter