the plc factory

have a overview

simens
s7-200,s7-300,s7-400
http://www.siemensplcweb.com/

ab
http://www.abplc.com/ab-plc.html
http://ab.rockwellautomation.com/Programmable-Controllers/Large-Control-Systems

mitsubishi
http://www.mitsubishi-automation.com/

omron
http://www.fa.omron.com.cn/product/ClassParent.jsp?class_DerectorId=0_655

xinje
http://www.xinje.com/products2.asp?FunName=%BF%C9%B1%E0%B3%CC%BF%D8%D6%C6%C6%F7%CF%B5%C1%D0&Qust=0_64_67

keyence(the doc is good)
http://china.keyence.com/products/plc/plc/plc.php