Sources for ubuntu ISO files
Drop .chef/plugins/knife/source_ingredient_windows.rb into your .chef/plugins/knife directory and run:
knife source ingredient ubuntu
:file_cache_path and :data_bag_path must writable and might need to be set in your knife.rb
The latest versions of ubuntu isos will be downloaded into your file_cache_path and your data bag path will get an ubuntu directory created which will be populated with data bag items for each version of ubuntu that is downloaded.