I just took some time to get all the checked baggage websites for major airlines that travel to Aruba from the US and Canada. USAir was not the only airline that is limiting to one without extra charge, so check your specific airline. Especially when you get close to departure... "Weigh" your options, sometimes it's cheaper to ship things to your destination ahead of your trip (sad but true).
United
Delta
American Airlines
USAirways/AWA
JetBlue
Continental
Air Canada