There are multiple ways to go about the funding you require – and it all depends on how much you need to make it worth your while and make sure the capital borrowed will be paid back. Like everyone mentioned here – venture capital or angel investors are a way to go, since both tend to think from a "future revenue" frame of mind as opposed to a banking theory of "what have you done so far?". If your company hasn't shown a history of a profit, banks may not be the way to go. While not all their programs require showing a profit, credit crunches can certainly affect what a bank can lend at the time. Since you have buyers lined up – taking on an equity partner may also be an option, if you know someone who may have the capital to lend. Whichever way it goes, it sounds like you have faith your product will sell – just make sure there's enough profit there to cover any investment and also allow you to keep control of your company.

It is hard to answer your question without knowing how much capital you need to raise, what you are bringing to market, etc. I'd agree with Brad though, venture capitalists are a good way to go. Also, depending on your patent, you may also want to look into various grants available with the government (check out grants.gov). If all else fails, loans are out there. If you don't have a lot of experience in this area, I'd recommend contacting your local SCORE group (SCORE.org). They may know of a local funding source which may be a good match for you and your company. Best of luck!

Or, if you've got customers already, go to a bank and get a loan. No risk, no reward.