So after a days work or so the theme is coming along, as mentioned before the theme is based on Twitter Bootstrap. The background image still needs some work, but my GIMP skills seems to have rusted a bit.
However I must say the responsive design extension to bootstrap is quite nice. (Why has it not been named adaptive design rather than responsive design?)
I have also added some sweet sweet Haml and Sass support. The Sass support was possible to implement via a Jekyll Converter, Haml however ended up as a rake haml task. The reason behind the rake task is the way Jekyll handles the _ folders, it does not process these folders, and it makes most sense to place my haml files in the theme folder.
The Sass converter is mostly based on a gist I found https://gist.github.com/960150. To enable Sass partials I had to specify my full theme path, however I am quite sure it is possible to derive it from the _config.yml or the Jekyll configuration. Also the Sass files have to start with a YAML Front Matter block in order to be processed automagically.
Other than than I have made a couple of small liquid filters, a read-more filter that triggers on <!--more--> and a simple or filter, which could be seen as an attempt to make a simple default to a piece of text if nil or empty.
Update Hmm it seems like my nice Sass trick makes Jekyll believe that my css file is a page :(