Before an employer hires a foreign worker with an H1-B visa, it must first fill out a Labor Condition Application(LCA). The LCA states that the position to be filled by a foreigner won't negatively affect the wages or employment of US workers.
The Department of Labor typically more LCAs than actual H1-B visas, meaning, an approved LCA doesn't indicate a successful hire. The data below shows which companies are most interested in skilled foreign labor, and where those jobs are located.
LCA data from My Visa Jobs, a service which aggregates government data from the Department of Labor. All data from fiscal year 2013.