The University of Missouri and University of Illinois jointly publish a 2007 guide to local St. Louis Area Farms that is available online: http://web.extension.uiuc.edu/regions/SIfamily/pdf/ToMarketDirectory_2007.pdf.
The Healthy Planet magazine and AgriMissoui hosts the 2008 html version of the St. Louis area To Market To Market guide on its web site http://www.thehealthyplanet.com/oct08_2008market.htm
If you are a resident of Illinois there is an excellent PYO/Farm Market site with powerful search capability at http://www.illinoisfarmdirect.org/index.html
Or consider the Illinois Market Maker directory http://www.marketmaker.uiuc.edu/