The antidote to the jagged aliasing is extra pixels
inserted on the edge. They are colors splitting
the difference between the two original colors.
Are times you don't want to anti-alias?
Smooth edges are nice, but sometimes they are to blurred. Small type is a good example. Anti-aliased small type can be too blurred to read well. There are fonts made specifically for no anti-aliasing and you will see them used on very small print such as the link lists often placed at the bottom of pages.
Setting the Photoshop Type control for "aa:" to none will create type with no anti-aliasing. You will have to experiment with fonts and sizes to get a good readable result.