Flight passes offer you the ability to travel extensively within a region, and are genrally going to be a cheaper way to go if you are travelling to many cities. However be sure you understand all the charges, as some pricing will not mention taxes or extra fees, and some have restrictions such as having to fly in and out of a single hub rather than directly from city to city.
Budget travel has a nice summary of passes:
POPULAR FLIGHT PASSES AROUND THE GLOBE
Pass: Aerolineas Argentinas South America Pass 800/333-0276, aerolineas.com.ar The Basics: Flights within South America priced by mileage, starting at $300 for up to 2,500 miles Heads Up: Date changes allowed for $25
Pass: Cathay Pacific All Asia Pass cathay-usa.com The Basics: Flight to Hong Kong and a choice of 18 Asian cities over 21 days, for $1,499 Heads Up: Join the free online club to save $200; booking through a travel agent is mandatory
Pass: BWIA West Indies Airways Caribbean Pass 800/538-2942, bwee.com The Basics: Flights between eight Caribbean destinations, from $450 Heads Up: Destination changes for $25; no backtracking allowed
Pass: Star Alliance African Airpass staralliance.com The Basics: Up to 10 flights in 17 sub-Saharan countries, at 15¢ per mile Heads Up: Only sold to passengers flying a Star Alliance partner into Africa