ok, forget about hitching - but stateside - you can inquire if there are any flights which are "deadheading" - which I think is the slang for simply traveling from point a to b with a minimal crew and that's it.
Sometimes they will sell you a ticket dirt cheap just to make a little something, but keep in mind no services will be provided, then again - if your hitching - you dont care about any services/
Boats??
If you're willing to work, you can probably work your way from point a to b, as free help is never a bad thing.
Someone mentioned 9/11, yeah everything changed after that, unfortunately for the worse...
Stowing away is probably a very very very bad idea, as these cats don't have a sense of humor anymore.
On a different note, there was an older couple who were traveling all over Europe - using either public transportation - or an AIRE Sea Tiger II, which they carried in a large soft case.
http://www.aire.com/aire/products/default.aspx?id=229
I know, it's expensive, but trust me - well worth it...
However, for those looking to do the public transportation / flying thing + kayaking, the Pakboats XT-16 definately fits the bill, just takes forever to put together.
Trust me, as I've got one of those too
http://www.pakboats.com/index.php?option=com_content&view=article&id=99&Itemid=148
Good luck in your travels............