What are the major world's stock markets?

Answer 1

There are a lot of stock exchanges in the world. As far as the major ones are concerned, those most often followed in the international media are as follows:

New York Stock Exchange (NYSE)
NASDAQ
Tokyo Stock Exchange
London Stock Exchange

Answer 2

Ten Largest Stock Exchanges by Market Capitalization (in trillions of US dollars)

New York Stock Exchange (soon to be combined with Euronext) - $17.8 [1]
Tokyo Stock Exchange - $4.8 [2]
NASDAQ - $1
London Stock Exchange - $3.5
Euronext (soon to be combined with NYSE) - $3.3
Toronto Stock Exchange - $1.83 [3]
Hong Kong Stock Exchange - $2.1 [4]
Frankfurt Stock Exchange (Deutsche Börse) - $1.4
Madrid Stock Exchange (BME Spanish Exchanges) - $1.1
SWX Swiss Exchange - $1.1

Other Large Regional Stock Exchanges by Market Capitalization (in trillions of US dollars)

Milan Stock Exchange (Borsa Italiana) - $0.94
Shanghai Stock Exchange - $0.92 (December 2006) [5]
National Stock Exchange of India - $0.76 (December 2006) [6]
Moscow Interbank Currency Exchange - $0.74 (September 2006)
Australian Stock Exchange - $0.73 (June 2005)
Bombay Stock Exchange - $0.73 (October 2006)
Korea Stock Exchange - $0.72 (October 2006) [7]
Bovespa - $0.67 (November 2006) [8]
Johannesburg Securities Exchange - $0.58 (September 2006)
Sources: Wikipedia article for each entry