Time Shares
Do your research, and join one of the Yahoo groups devoted to this topic to hear strategies. I work with a gentleman who goes to Cancun for a week each year with his family for free by knowing how to play this game. On the last day of his trip, he goes to a presentation and works the salesmen until its time for him to "go to the airport to catch his flight home". They are so anxious to close that they give him a return trip voucher good for 12 months.
In addition, by going through the presentations so many times now, he knows their sales routine and pricing better than the sales guys he gets each year. He finally bought into one, but only after negotiating a price that was below their cost for an entry level 1-bedroom and upgrading himself to a penthouse corner 2-BR unit.
Not suggesting that everyone is capable of this, but if you have the time and patience to work the system, you can get alot of free trips and excursions and end up with a sweet deal if you want it.