Being in the position of looking for a visa for my startup, I've informed myself. The way to go right now is to apply for an E2-Visa, which is granted to foreign entrepreneurs owning 50%+ of their company and having raised $100,000 and up.
The $100,000 sum is not written explicitly in the requirements of the visa, however I have talked with immigration lawyers and they've told me at a sum of $100,000 more than 9 out of 10 E2 visas are granted.