A plugin for Jekyll that adds files for each post.
git-archive --format=tar --remote=git://github.com/indirect/jekyll-postfiles.git master | tar -xf -
When you have a file you want to include in a post, create a directory named after the post in _postfiles, and put the file in there. Here's an example directory structure:
_posts/
2010-09-06-jekyll-postfiles-plugin.md
_postfiles/
2010-09-06-jekyll-postfiles-plugin/
file.zip
To refer to the file inside the post, use the postfile liquid tag, like this: {% postfile file.zip %}.