If you find yourself repeating the same text over and over, Apple provides a text substitution feature in Mac OS X. Go to the Apple menu > System Preferences > Language & Text > Text. Enable “Use symbol and text substitution” and create any new “shortcut” that will automatically be expanded into longer text. I like to precede my shortcuts with a slash so that I don’t accidentally insert a long string of text.
If you need more advanced text substitution (formatting, the ability to choose items from a menu…) check out TypeIt4Me ($4.99 Mac App Store) or TextExpander ($34.95).