I have a selection I want to enlarge using nearest neighbour. I don't want to scale the whole image, just a selection. Is this possible?
Ok, I've worked this one out. Photoshop has a single, global setting to determine the scaling algorithm used, for everything. It is in Preferences > General > Image Interpolation. Setting this will make all image scale transforms use this algorithm.
So set this to nearest neighbour, perform the scale, change it back, is the rather tedious solution.
UPDATE FOR CS6: In order to change interpolation in Free Transform mode, one must select it from the options bar when transforming. The setting in preferences now has no effect on Free Transform.