Alfred is an amazing workflow management app for OS X. SourceTree is an amazing graphical client that allows you to interact with your Git and Hg repositories without needing to use the command line. By combining the two, you can save tons of time in your normal development workflow.
Locate Source Tree.alfredworkflow in Finder and open it to import it into Alfred. Select a category and click "Import".
Opening a specific repo - the shortcut to use is "st repo_name":
Listing all repos - the shortcut to use is "st" (no argument provided):