Cuba charges CUC25 departure tax on international flights. Cuban check-in staff often scam foreigners by attempting to charge an excess baggage fee where none should apply. Know your legal allowance (which varies between airlines). Try to use a counter with a visible scale screen and check that it is properly zeroed before your bags are put on.
Cuba prohibits the export of valuable antiques and art without a license.
Returning to the United States: U.S. citizens who have traveled to Cuba are not allowed to bring back any Cuban purchases, regardless of whether or not travel was licensed. The exception is literature and other informational materials. All other Cuban goods will be confiscated, wherever acquired and regardless of value. These restrictions apply to citizens of any country arriving from any other country, including in-transit passengers; contact the U.S. Customs Service (1300 Pennsylvania Ave. NW, Washington, DC 20229, tel. 703/526-4200, www.cbp.gov/xp/cgov/travel [1]).
Returning to Canada: Canadian citizens are allowed an “exemption” of C$750 for goods purchased abroad, plus 1.14 liters of spirits, 200 cigarettes, and 50 cigars. See www.traveldocs.com/ca/customs.htm [2].
Returning to the United Kingdom: U.K. citizens may import goods worth up to £340, plus 200 cigarettes, 50 cigars, and one liter of spirits. See www.hmrc.gov.uk/customs/arriving [3].
Returning to Australia and New Zealand: Australian citizens may import A$900 of goods, plus 250 cigarettes or 50 cigars, and 2.5 liters of spirits. See www.customs.gov.au/site/page.cfm?u=4352 [4]. New Zealand citizens can import NZ$700 worth of goods, 200 cigarettes, 50 cigars, and three bottles of spirits. See www.customs.govt.nz/travellers [5].
Links:
[1] http://www.cbp.gov/xp/cgov/travel
[2] http://www.traveldocs.com/ca/customs.htm
[3] http://www.hmrc.gov.uk/customs/arriving
[4] http://www.customs.gov.au/site/page.cfm?u=4352
[5] http://www.customs.govt.nz/travellers