These are the extensions that I'm using for my personal blog at BrianMcMurray.com.
These are based off plugins from RFelix, Jose Diaz-Gonzalez, and Roger Lopez.
These extensions use jekyll_ext, which allows you to extend the Jekyll static blog generator without forking and modifying it's codebase.
With this code, not only do your extensions live in your blog directory, but they can also be shared and reutilized.
Use these extensions with jekyll_ext by just cloning this repo into the _extensions dir of your blog: git clone git://github.com/bmcmurray/my_jekyll_extensions.git _extensions
More information about jekyll_ext can be found here: Jekyll Extensions -= Pain