I'm looking for a open source alternative to TextExpander (or TypeIt4Me or Typinator) -- not because I'm cheap, but because I'm interested in the source code. It therefore doesn't have to be as polished as the apps mentioned above.
KissPhrase is an open-source, free, working (as of September 2013), text expander tool for OS X. I'm using it on OS X 10.8.5 Mountain Lion.
You can check out the source code with
svn and download an installable disc image from the project home page at https://code.google.com/p/kissphrase.
It's not as feature-rich as the other tools you mention, but is definitely something check out if you're holding off on buying TextExpander, TypeIt4Me, or Typinator (as I am).
The only issues that I have noticed with it are that it doesn't substitute perfectly in Terminal or iTerm, and doesn't seem to work at all in Alfred, Spotlight, or search fields.
You may want to rebuild it for x64, in which case see this answer for how to get KissPhrase to compile in Xcode under Mountain Lion.
If you are looking for an alternative or a free alternative(not open source though) try xType for Mac by adnx software. http://www.adnx.com/i/apps/xtype4mac . As much as I loved using Text Expander trial version, it is overpriced for me (would had considered under $10) - for the cost of a utility, it is more expensive than the cost of the Operating System on a mac.