Yes they do. For more information see the related link.
limit size of bag
free but the second bag costs money
No currently Delta Airlines does not charge for carry-on luggage.
At a delta-v of 10mph
According to Delta Airlines' website, one bag is checked free for flights to Aruba if the ticket purchase date occurred before June 1, 2011.Specifically, a baggage fee of $27 is assessed on a second bag for tickets purchased online. A baggage fee of $30 is assessed on a second bag for tickets purchased at the airport. Additional fees are applied if the size and weight of the checked bags exceeds restrictions.
The first bag is free when traveling with Delta internationally. Whether you get a 2nd bag for free or not depends on what countries you are flying to and from. It also depends on whether you are a medallion or flying in a premium cabin. Delta American Express Cards do not get you a 2nd bag on international flights. Those cards only affect US domestic flights. All the rules are on Delta's website at the related link.
Delta Charged $25 1st Bag, $35 2nd bag and $125 3rd bag on 6-9-2012
The standard charge is 25 dollars unless the bag is over sized or an unusual shape and size.-
Yes you can if you put it in a plastic bag or a little zip-lock bag. See for more details under the related link.
Purchasing baggage tickets to check your baggage with Delta airlines can be done through Delta's website. Delta's website has information about check-in options including how to pay for baggage fees. It's best to be very cautious of other websites that would try to sell baggage tickets.
United Airlines charges baggage fees of $25 for your first checked bag and $35 for your second bag. They do not charge for carry-on luggage, but it must meet their policies. United will also charge up to $100 more per bag if they are oversized, weigh more than 50 pounds, or you are checking more than two bags per person. International fees for baggage start at these same rates, but can be higher as well.
Most airlines now charge astronomical luggage fees to check even one bag. One can avoid the long lines at the counter and the baggage claims but packing the essentials in a duffle bag. Most duffle bags will fit just fine in the overhead compartment of the airplane. Be sure that everything packed adheres to TSA regulations.