Varies an awful lot by part of the country you are in - can be as low as $50-60/SF for an extremely cheap home in parts of the midwest and deep south, to no less than about $200-250/SF in ritzy sections of major cities.
Depends also, of course, on foundation - can be $20-40,000 cheaper to build on a slab on grade in frost-free areas than to put in a full basement in deep frost penetration areas.
National average, according to latest available National Associaiton of Home Builders info, is about $125/SF excluding land but including utilities - here is a link to a bunch of data for 2011 (last tabulated year) and about 5 years before that -
Per square foot numbers do not really tell anything like the whole story - and be careful about comparing between areas, because in some cold climate areas marginally heated garages (kept in 40's or 50's rather than 70 or so) are not counted in square footage, and in some areas, especially where basements are subject to flooding like in floodplains, basements are not counted in square footage either unless they are fully finished at time of listing. Also, the smaller the house and the more spread out it is, the higher the per square foot cost relative to more compact, multi-story houses where you are paying for less foundation and roof per square foot of living space.