Shape Layers. Strokes. You know how they work-- add a stroke, and it'll increase in width both internally and externally from the path. But what if you want to preserve the outer edge of your path, adding strokes internally only (a la Illustrator?)
Here's a quick little preset that'll add a pseudo "inner stroke" to your shape layer. Now, there's no "official" way to do this, so it's a hack and a half that uses offset and some expression magic to simulate it. Depending on how tight your shape corners are this can break things a little, but otherwise it's pretty solid.
Apply the preset to your shape layer, and it'll add in an offset and a new stroke. The only things you need to worry about here are
stroke width and
stroke colour. Duplicate "Inner Stroke - Stroke #X" to add more inner strokes to the stack, however the more strokes you get the more likely it is to produce strange results.
Download and play!