In the course of trying to jazz up the text in my current game, I came across a great little tool for generating XNA Spritefonts with various effects added. Effects include outlining, beveling, dropshadows, and texturing.
It generates a .png file that you add as content to your project using "Sprite Font Texture" as the content processor rather than "Sprite Font Description". In code, you load it just like any other SpriteFont.
You can find it here.