Check into companies that supply the government. A great example in your area is Boeing. Boeing has a large defense systems facility in St. Louis.
Boeing: Integrated Defense Systems Home
In the engineering and comp-sci fields, you'll find that most workers have a disdain for professors/universities/... because of how impractical a lot of what they teach is, and will be more than happy to try to help someone get a leg up before the teachers screw them up too badly. They are also frustrated that people coming out of college have "no freaking clue about the real world." Appeal to that.
At these places, don't call the front desk. They seem to have a reflex to hang up on you. The interesting thing about internships, etc. are that the college students can't find them, and the companies can't seem to fill them. Best strategy that I have heard so far is to go to the facilities around 10am, and look for the people standing around having a smoke break. Tell them that you are a comp-eng geek in college, and looking for some real world experience to help you make sense of what the professors are feeding you. Tell them that you would like to learn from the people in the field how it's actually done vs. what the ivory tower people are telling you.
That's my advice... Do with it what you will.
--Curt