According to a Reuters article on MSNBC.com, it looks like Jamaica is going to get its first female prime minister, Portia Simpson Miller. From the "Worldwide Guide to Women in Leadership," a summary of the current female heads of state and government:

There are 191 members of the United Nations and a few independent states outside. 17 have got female leaders.

Of the monarchies, there are reigning Queens in Denmark, The Netherlands and the United Kingdom - and the latter is represented by female Governor Generals in Canada, New Zealand and Saint Lucia, who function as their countries' de-facto Heads of State.

The 5 female Presidents are in Finland, Ireland, Latvia, Liberia and The Philippines. And a President-Elect in Chile who takes office in march

There are also 5 woman Prime Ministers; in Bangladesh, Germany, New Zealand, Mozambique and São Tomé e Princípe and women are designated to take over as chiefs of government in both Jamaica and The Netherlands Antilles.