If I had the money and the space, the USA-made Retsel Mill-rite grain mill would be my first choice, due to it's versatility (cracked grain to fine flour). I tracked grain mill reviews for about 20 years (mid 1980s to mid 2000s) and the Retsel consistently got good reviews for quality construction and durability. The Retsel Mill-rite has an electric motor, which is really required for milling grain in any quantity.
If you don't specify preference, the Retsel ships with stone ceramic grinding plates, which are suitable for most types of grain. To mill oily seeds (such as legumes, nuts and *field corn*) the optional stainless steel grinding plates may be purchased.
At about $400 retail, this grain mill is for the serious home milling enthusiast. While advertised for "home use", I would think this unit might also be suitable for a small, specialized bakery or a coop that wishes to mill grain for it's members.
Retsel's home page for their Mill-rite mill is here
Two reviews of the Retsel are here
At times this unit does appear on eBay and generally sells for considerably less than retail. If you're not in a hurry to buy and are comfortable using eBay I would recommend it as a possible source.
======== update Apr 29, 2008 ==========
======== going price for a Retsel on eBay ========
A Retsel Mil-rite electric mill sold on eBay for $275 (plus shipping) on Apr 22nd. The mill came with an extra large hopper to hold grain.
I was curious what people were willing to pay for a USA made Retsel so I tracked the auction. (I have no connection with the seller.)
I'm posting a link to the auction's photo of the Retsel, though the link may not work after a week or two.