For Junior Project, I and three other students created a Ruby on Rails web app for collecting recipes. Like other recipe sites, it let you publish your recipes, but only ours let you clone and tweak other users’ recipes to make them your own. It also maintained links between original and derived recipes, so everyone could see which recipes inspired which.
The site featured a restful JSON API, as required by our clients.
Originally, we planned on having convenient features such as nutrition and measurement conversion for ingredients, but we had to cut them from our scope. Ingredients are just stored as plain text now.
The site is no longer running.