Davis was the 25th overall pick in the 2009 draft, and his signing clearly was helped by the fact that the 24th (Atlanta's Peria Jerry) and 26th (Green Bay's Clay Matthews Jr.) picks both signed on Thursday.White's contract negotiations might be a little trickier because he's a quarterback, and those players don't always fall into slots based on the picks before and after them.
As for Clemons, it's a little surprising he remains unsigned considering how late he was drafted. He has a chance to get a big role as a rookie, so it clearly would be disappointing if he were to miss a number of practices.