The status of Cuba's main industries

Tourism. Now the economy's largest source of revenue, tourists—primarily from Canada and the European Union—bring some $2.1 billion into the country.

Remittances. Academic sources estimate remittances total between $600 million and $1 billion a year, most coming from families in the United States.

Nickel. Cuba has the third-largest nickel reserves in the world. Nickel is currently the country's biggest export, bringing in roughly $800 million in
2004.

Sugar. Sugar was long the primary industry in Cuba, but production has plummeted due to outdated factory equipment. In 1989, production was more than 8 million tons, while the harvest in 2004 was only 2.3 million tons.

Foreign investments. Cuba receives hundreds of millions of dollars in foreign investments from Venezuela (some $900 million in 2004), Spain ($700 million), and China ($340 million).

Which I got from the following link, a short, solid summary of US/Cuba international relations:

http://www.cfr.org/publication/11113/