Right now I've got a tagger UI and an API that correctly identifies foods you've tagged (from the USDA Food Nutrition Database) and processes gram-amounts from plain text to produce a combined nutritional chart.
This is very early stage so more of a call for help: the nutrient chart needs a better design and the API needs work in properly processing g/mg/ml and all the weight conversions defined in the usda_weights table.
If you're into nutrition, liked the project and would like to help, drop me a note.