Together with a friend from Caltech, I've helped create a social content network for food information which supports semantic search for food information. For example, you can go to efoodi.com and search for 'meat', 'vegetable', or 'Mediterranean' to get a glimpse of the concepts it understands. It also supports social search and tag-based browsing. These technologies are powerful and it's surprising they're not more commonplace on the web.