Snippets by Conceited Software is a US$5 text macro application for the Mac. Define a shortcut such as "mas" to have it automatically expand to "Mac App Store" or other words, phrases and even entire paragraphs of text. You can even include rich text, such as bold, italics and images.
I've been using Snippets for the past few days instead of my usual macros program, TextExpander, and I have to say I'm impressed. The interface is clean, replacements are fast, and a recent update added "placeholder" text so that you can have Snippets pause during expansion for you to enter in some text, such as someone's name. It's a great utility that does what it says it will.
Coming from TextExpander, there are some features that I definitely miss, such as Dropbox syncing, the ability to automatically add the current date or time and, yes, even the little sound that TextExpander plays when it expands a shortcut (full disclosure: my wife hates the sound and hopes to never hear it again). Then again, TextExpander (previously Textpander) has been around since 2005, whereas Snippets is only a few months old. I fully expect it will get better and add these features, but remember my rule for buying software: buy it only for what it does today, not for what you hope (or developers say) it will do tomorrow.
If you already own TextExpander, TypeItForMe or Typinator, you don't need Snippets. However, if you have been in the market for a text macros app but have been put off by the cost -- $35 for TextExpander, €19.99 (about $27 as of this writing) for Typinator or $20 for TypeItForMe -- Snippets might be just what you are looking for. Its biggest shortcoming right now is that there is no way to export your shortcuts, so if you use more than one Mac, you'll have to enter them separately on each Mac.
Snippets is available exclusively through the Mac App Store.
UPDATE: The 1.2 release of Snippets (4 Feb 2011) added the ability to insert current date and time into shortcuts, as well as fixing the "tab order" bug when moving through input fields with the keyboard when creating a new snippet.