The Koenigiss posted a time faster than 250 but it was unofficial since it has to make it both directions down a track and average. However, shelby is building the SSC which so far has posted 256mph...
http://www.shelbysupercars.com/press.php
That link goes to the press release on the shelby site that says it broke the official record currently held by the Koenigsigg and the unofficial record held by the Veyron.
William