[SophieLeeds]

What do I package fleece in for posting? Is a cardboard box alright?

They are 100% dry

[SallyintNorth]

I discovered last year that transporting fleeces in hot weather may cause them to sweat and hence felt, so would avoid plastic bags or anything that doesn't breathe.  (And if you must use plastic, make some airholes.)

In other than very hot weather, I put them in a polyproplylene sack inside a cardboard box.  In hot weather I don't now send them at all if I can avoid it, but if I had to, I'd use a cotton pillowcase inside the cardboard.  I might make breathe holes in the cardboard, too.

[SophieLeeds]

Thanks Sally, pillowcase in a holey box it is 

[Fleecewife]

I send mine in woven polypropylene sacks, with the top carefully tied so it doesn't catch in the postal machinery.
You can write the address on the sack.