I’m building an AutoTag system for my Jekyll setup. Unlike the Zemanta system I use for additional keywords, this tool is designed to match your content to existing tags you already use on your blog, helping to keep a consistent taxonomy and better post relationships. It’s more like the TextMate/WordPress version I created. Like that version, there are two parts to it: a tag plugin on the blog side and a local tool for pulling information from it and processing it.
Note: this tool could technically be used on any static blogging system that uses YAML headers. Generating the JSON listing of your blog’s tags would be the only part that would need customization.
It’s working great for me, but I haven’t tested every possible scenario yet. Make sure you have a backup of your posts (or just test on copies of your _posts folder). I use git for versioning my Jekyll source files, so I can always undo a mistake. It’s worth it.
Check it out in the Projects section.