First, if you are still a student, then there are numerous contests that will provide scholarships, and sometimes cash, for winning. Check out the collegiate inventors competition and the NCIIA.
If you are out of college and you still would like funding, you can do a few things to help make your idea a reality. First, starting a business and obtaining a business loan is a very good way to get financial backing. The downside is that you will need to pay this back eventually, so if your idea fails, you could be on the hook for thousands of dollars.
Government grants are another method of getting money. The upside is that you can get a good bit of money, and you don’t have to pay it back. However, grants like this can be extremely competative, and you have to make sure that your invention covers an area where a grant is currently open.
If you have some connections, you can also try to contact a venture capital firm – they will invest and fund your invention in order to bring it to market. The downside of this is that they’ll want a share in the profits, and they may want to become more involved, which can comprimise your original vision.
While it is difficult to get financial help to make your invention a reality, it is definately not impossible.