For most programmers, there's the H1-B Visa. This is tied to a specific employer, they're given out on a roughly first come first serve basis and there's a quota of them: only 65,000 are given out per year at last count. Last year there were so many people applying that all the visas for FY 2008 (starting October 07) were given out on April 1st -- the next time you'd be able to apply would be April 1st 2008, for October 2008!

For Canadians and Mexicans there is a different visa, called the TN, created under NAFTA. If you read the NAFTA proceedings, you'll come to understand that the method of getting verified at the border was meant to make it easier and quicker to get a Visa, for certain classes of professional. The one professional category involving computers, 'computer systems analyst', was so vaguely defined that one could only interpret it was meant as an umbrella term.

But what's happened in reality is that small-minded border guards have been given the authority to simply reject people. They demand all sorts of things that aren't in the law, and they make no apologies.