Most college fine art programs have ceramic shell and bronze or iron casting facilites. Typically you can find someone at these schools to cast some work for you, like a student or resident artist, if you call the professor and ask them for a referral. Having work cast this way is usually at least half the cost of going to a commercial art foundry.
I've worked for art foundries and colleges, and I'd have to say going to a commercial art foundry should be your last resort.
You haven't really specified what it is that you're casting, I can understand if you want to keep your project under wraps, but they type of metal casting you will need is directly dependent on the size, shape, and complexity of what you want to have cast.
Is it bigger than a shoebox, or smaller? Is it hollow or solid? Is it smooth, or intricately detailed? Your answer to each of these questions can determine the best method of metal casting for your project.
If you need some discrete advice via PM, I'd be glad to help. I've got over 15 years in this field.. so I think I could point you in the right direction.
