Let Photoshop Straighten Your Crooked Scans
That’s right—straightening is totally automated in Photoshop. In fact, try out this ideal situation: Toss two or three photos casually onto your scanner bed, without taking the time to carefully align them, and scan them all with just one pass of your scanner. Then, open the single scan of the three photos in Photoshop, go under the File menu, under Automate, and choose Crop and Straighten Photos. Photoshop will then crop, straighten, and even put each photo into its own separate document. Nice.