SocialWall.me - Collect, analyse & broadcast your social media posts
Thunkable - Powerful but easy to use, drag-and-drop mobile app builder.
SocialRank Market Intelligence for Twitter - Enter any handle. Sort & filter their followers. Try @pmarca
BuildFire - BuildFire is the easiest way for small businesses to build a mobile app in a matter of minutes for iOS and Android.
Hosting Checker - Find out the hosting provider of any website
MIT App Inventor - App Inventor is a cloud-based tool, which means you can create apps for phones or tablets right in your web browser.