If ALL the fluids have been removed, and you have harvested any part you want, you could use the trailer to take it to the local landfill. They charge by weight. In my area a 2000 lb boat carcass costs less than $50 to get rid of. However, it only weighs that little without an engine and without a keel (which is sold for scrap value). The bulldozers at the landfill make short work of the hull, and it is just pieces when they cover it up.
The ones I've cut apart I've used a sawzall on, but it will use up blades. Chain saws generate more dust than sawzalls, in my opinion, and angle grinders just dont get into places that I have had to get into. However, this can be a LOT of work, and all you are getting out of it is a free trailer.
Consider centerline's idea in post #8. It's a lot less effort, and may put cash in your pocket. Another great alternative is to donate it to Sea Scouts. If it is an active chapter that rehabs boats regularly to fund their racing and organized trips, they will know what it is worth, and will write you a receipt for a charitable donation. If you itemize your deductions, this may be worthwhile, and they would likely come get it (though you would have to make it clear that the trailer is not part of the donation).