A very common way of doing this sort of thing in stable environments. California just floated a few billion dollars worth of them in the last election. Borrowing money from citizens for (ostensibly) worthy projects. Unfortunately, most such things open themselves up to pork festivals, since it allows the government to spend money that it doesn't have to raise taxes for. At least not right away.

I don't know if there are good ways to do this in poorer countries that don't have stable economic infrastructure in place. A bond is a recognition that the government will still be there some years from now to pay you back. This is not an insignificant issue for some countries.