The MIT App Inventor is a free app development tool that has been available for free for the last decade. It's a great tool to use to introduce students to some programming concepts while letting develop apps that they can actually use on their phones. While it might seem complicated at first glance, after they have mastered a few basic concepts students can create some amazing applications through the MIT App Inventor.
This morning I used part of my snow day to create a video tutorial on how to create your first Android application through the MIT App Inventor. Watch the video then try making your first app. Or watch the video in one tab while following my instructions with App Inventor open in another tab.