On eBay there are usually several Hawaiian Vacation items on sale like timeshare rentals, condo rentals, full vacations with airfare, general coupon booklets, lava-covered property, a week at a hotel, tours, and actual vacation homes. I have never bought travel off ebay, so I can't give you any advice on legitimacy, but I have spoken to a couple who bought a kauai helicopter tour from ebay for a good price. They received a certificate and had no problem redeeming it when they got to the island. You also can check at the ebay travel forum for known scams and advise: Ebay Travel Forum

Suggested ebay searches: Hawaii vacation -- Hawaii Tour -- Oahu -- Maui -- Kauai -- Big Island

Note about the coupon booklets - most of these are free once you get to hawaii, pick them up at the airport stands or your hotel or at the local mini mart - so don't pay for them unless you want them before you get here - leave me a comment via the link at the bottom if you want to know if the one you are looking at is free.