There is a range of Windows based and online software available :
http://termitesapp.com/ is Windows and their is a free trial although the full version is $34.95. The class seating plan software offers a wide range of features such as details of a pupils’ ability and their preferred location in the classroom.
http://teacher.scholastic.com/tools/class_setup/ is online based so can be used from any web browser. The work area is kind of cramped but it comes with a range of ready to drag classroom furniture.
http://www.superteachertools.com/instantclassroom/seating-chart-maker.php is another online tool with an easy drag and drop interface but it is rather plain and uninspiring. The layout options are also rather limited and there is no option for additional information about the pupils