Resource for ballparking current home construction costs?
As a former construction estimator, I would suggest that you get in touch with the contractor sales department at a building supplies store in the area in which you're considering building.  Quite often the estimators there will have a ballpark "per-square-foot" price for materials, and may have an idea of a ballpark price for labour, too.  They can probably refer you to reputable builders as well.

That said, there are really far too many variables for a ballpark estimate like that to be at all useful.  You can get a house to lock-up fairly cheaply, but it's the finishing work that's really going to determine the end cost.  The cost of a beautiful metal tile roof is going to be a lot more than 20-year asphalt shingles, and the cost of vinyl siding is going to be a lot less than stone, as examples.

To get any kind of accuracy in an estimate, you're going to need to have a set of plans and you'll need to decide what exactly you want in terms of finishing, land, appliances, etc.  Anything shy of that is really just going to be pulling numbers out of thin air.