Best/Cheapest way of mailing boxes?--Question ANSWERED, thanks--

[dougscats]

I'm in the process of moving, cleaning out closets and attic, and want to get rid of some stuff rather than move/store it.

I normally use the UPS priority mail, flat-rate boxes. But sometimes the cost of shipping is too expensive, e.g., for books.
I checked out ground shipping rates from UPS online, and the rates seemed a bit cheaper, but it also seems to me that anytime I've tried to ship UPS ground in the past it's been pretty expensive.

Anyone with experience who can give me advice on the best way to mail boxes?

Thanks.

Doug