In PS you can have your stroke be a gradient. The default is Linear but there is Radial, Angle, Reflected, Diamond, and Shape Burst. Say I have a 10 pixel stroke with a black to white gradient...linear will put the white at the top and black at the bottom, radial will create something circular where the black is like a black hole with white at the edges forming a ring, angle works like clocks hands going around starting with black at midnight and going around getting lighter until white at 11:59, reflected will have white at top and bottom with black in the middle, diamond is like radial but instead of using a circular shape it uses a diamond shape, shape burst runs the gradient from black to white from outside in (similar to radial but in the opposite direction) but it keeps the shape of the object...this is sort of like increasing a selection size 1 pixel at a time...so that the stroke itself is white where it is closest to the object and black furthest out. This is very handy for making beaches (not as good as outer glow though) or black rings around a landmass on a parchment-style tan and black map. The stroke can also be applied outside or inside the object as well as centered on the edge. Lastly, you can also use a pattern as a stroke instead of a solid color or a gradient. The only downside is that the stroke does not fade out like an outer or inner glow. The following pic should explain it better.