There is currently no available visa to support immigration into the United States with the intention to allow you to launch your company.
As you can see from the other questions/answers on here which address this issues there are people who try to develop work-arounds. They enter the United States on a work visa or a student visa and attempt to launch their company during their available time. All of these carry risks as they are often violate tenets if not intentions of their Visa.
The proposed "Start-up" visa would be a very valuable option. It is a long way from becoming law. While support is growing, items such as this -- especially in the context of a Presidential election cycle -- can take a long time to pass. And unfortuently the issues surrounding immigration are extraordinarily controversial and even when framed in a pro-business, pro-jobs, pro-development context many elected official are afraid to touch it because it is associated with the word "immigration."
I have had the opportunity to work with several start-ups that have received funding in association with the US EB-5 visa. The EB-5 Visa promotes business and job development in the United States by providing a qualified investor (and their immediate family) a Green Card in as little as 90 days for making a qualified investment in a qualified business in the United States.
A qualified business is one which is approved by the USCIS. A qualified investment is one that meets the USCIS requirements (for example it must be an "at-risk investment"). A qualified investor is one that meets the USCIS requirements (including demonstration that the source of money was legally obtained and has had all relevant taxes paid).
The primary qualified for the program is that the investment must generate 10 pernament positions. With a $1,000,000 investment these 10 jobs must be direct W-2 positions. With a $500,000 investment these jobs can be direct or indirect. A $500,000 investment must be made in association with a USCIS-approved Regional Center.
The relevence to you in the question above is that with an apprpriate US partner the business receiving the investment could be your start-up. The EB-5 Visa issues a conditional Green Card -- and if requirements are met upon review in 24 months-- the conditionality is lifted. And as a Green Card holder -- either conditional or permanent -- you can subsequently work for the business.
Obviously there is a tremendous amount of additional rules, requirements and processes associated with this VISA -- but if you have the resources (or someone qualified gifts them to you) to successfully launch your start-up in the United States, this may be an option for you.
Added: (The below was added in response to Alan's comment below)
While I do not have personal experience with an EB-2 Visa being successfully used by the founder of a start-up, I do know folks who have used it to secure needed talent associated with their "start-up." These start-up had been fairly well established if my memory serves me correct. The EB-2 Visa is based on a specific job associated with a sponsoring business.
An existing business files for approval. The challenge is that the business must be qualified. The chatter is that the company needs to have a 4 year track record and 10 million revenue to support the I-140 application. This usually involves demonstration of financial history, existing employees, etc. The purpose of this is to limit the fraud associated with shell companies launching with the purpose of sponsoring a Visa.
As a start-up you will be under particular attention to this matter. Having significant investment, clients, and employees as part of your launch may mitigate the lack of tax, fiscal and employment history.
The visa is then associated with a particular person. The individual must be a professional with an advanced degree and at least 5 years of progressive experience in that profession. There is also an option for qualification based on "exceptional ability" in science, arts and business. Who know exactly what will be determined exceptional ability, but a good immigration attorney can always make a good case! There are additional rules about equivalent experience and such.
One of the challenges with using this visa (over the EB-5 above) is that the sponsoring employer does so through the labor certification/PERM process whereby, the US government determines whether qualified US workers can fill the open position. The current status of the economy and unemployment can make the PERM case for a employer that they need to secure you specifically and that your particular skills are not available in the US a challenge.
Unlike the EB-5, the EB-2 visa is job related and does not provide a direct option for securing a permanent Green Card.
Most immigration attorneys I know would consider the EB-2 a poor visa choice for a traditional under funded, just launching start-up -- so much, they wouldn't waste your time taking the money. It is the lack of an existing visa to meet this particular need that creates the environment for the proposed "Start-up Visa" in the first place.