Maybe a website that connects all your social media accounts and show you important updates and messages from all of them at one place.

If you want to build something for bitcoin community and you are a experienced web developer, you can make a stolen bitcoins database, where users can post their wallet addresses and a proof of ownership and it should allow them to explain how they lost their bitcoins and they should be able to track their funds or get notifications when funds are moved. If it works properly I think exchanges can use it's Api to identify stolen funds/deposits.