Breevy ($30, 30-day free trial) allows for creating abbreviations that, when typed, can substitute in a block of text, launch a program, or open a Web site.
For example, you can create a 'sig' abbreviation that will automatically substitute your full e-mail signature for 'sig' when typed. Or an 'ffx' launcher that will fire up the Firefox browser when you type those three characters.
You can define any given abbreviation so that its substitution or command runs automatically when you type the abbreviation, or require that you also type a certain trigger key that you choose (CTRL by default). Or, you can choose to use any given word-ending character after the abbreviation (such as a period or comma). It's quick and easy to create a new abbreviation or launcher.
Compared with similar utilities such as the Enso Launcher, Breevy appears more focused on substituting text. If you frequently type out the same sentence or block of text, Breevy would likely save you a fair bit of time. However, unlike Enso Launcher, Breevy isn't free. After a 30-day trial it will run you $30.