microblogging website social media like twitter/quora reddit.com ecommerce website (will be heavy) recipe sharing website (will have upvotes/downvotes for a recipe, comments and pictures, trending recipes, new recipes, categorized recipes) livejournal (http://www.livejournal.com/) meetup.com
Some ideas for students: [Get in contact with some Android students, you can make a project collaboratively] A website which helps you create another website [like wix.com] A blogging engine Something which solves your problems Resume builder website [get some examples] You can build a rails gem Reminder website [set a reminder and forget, you just need to verify your email account] Something like evernote Single website which posts on all your social media accounts Social media website for managing our course wherein students from different batches can interact
#Keep adding ideas to this by sending me pull requests