i got a frame shipped to me from CA (i live in toronto)
+1 on the previous suggestions on using USPS.
and some buyers will ask you to understate the value on the item to avoid super high duties.
if you feel okay doing that i suggest you declare it as "used parts" and please place it in an unmarked box.
then MAKE SURE you give it a reasonable estimate. or else Customs will open it and go "yeah RIGHT this is worth $5" and slap a HUGE duty on it.
my Jamis frame was shipped in a marked cannondale box with a $5 value on it. Customs decided the frame itself was worth $1200 and therefore I owed $200 in taxes.
so please do yourself and the buyer a favor and be smart about it.