In addition to my comment i post an interessting paragraph from snowleopards FAQ:
I read that Snow Leopard includes a typing shortcuts (text substitution) feature, but I can't find it. How to I turn it on?
In System Preferences, click the icon for the Language & Text pane in the top row (known as the International pane in Leopard), and then click the Text tab. The scrolling list on the left includes a number of default text substitutions (to turn (c) into a copyright symbol, for example), some of which are turned on by default. Click the + button at the bottom to add new substitutions of your own, and click the checkbox next to each item to enable or disable it.
Note that this list is global -- there is no way to create application-specific substitution sets -- and it is currently only used by a few applications, such as TextEdit and Mail. In those applications, substitution can be turned on and off for all documents or for individual documents.
This Paragraph can be found here:
FAQ