Men's business casual - can be as diverse as women's business casual... Some offices Polo Shirts are considered business casual, other offices, business casual is still wearing a tie, but not a suit...
but on the more "wall streetish" end it's Docker's style pants, preferably in darker colors, and neatly pressed, shirt would be a button shirt, not necessarily in a solid color, you can play a little with the trendier prints, tucked in, belt, shoes could be tassel loafers, or just plain loafers.
This site from the Virginia Tech gave some pretty good guidelines
http://www.career.vt.edu/JOBSEARC/Bu...ATTIREMENWOMEN
Shoe selection here:
http://www.shoebuy.com/sb/s.jsp/r_ss....6281-96.78524
Stores like Mens Wearhouse should be a good jumping off point for you to pick up some basics, and even catalogs like J Crew or Eddie Bauer might have some appropriate clothes.