Even simpler option:
1. Find a font you like. Something Arial or Bitstream Vera works well for this task.
2. Now goto your World of Warcraft folder and create a new folder called Fonts.
3. Drop your selected font into that folder.
4. Right Click on the font select "Rename" from the pop-up menu.
5. In the field that pops up, enter this name:
MORPHEUS.ttf
6. Start WoW and enjoy. This will overide all usage of that font. No AddOn is needed.
You can use this method to override all of the fonts in WoW and most of the custom UIs (that I know of) use this method. Alternately you can use mods like mentioned Fontain or Tekkub's AddOn,
tekicles. For fine grain control there always
ClearFont2 however I find CF2 to be a bit large for my tastes.