DC Metro Arrival Times
I wanted a break from web programming and ended up liking Android development way more than I thought I would. This is app performs one simple function. It displays estimated arrival times for trains in the Washington DC Metro System. There are apps that do more, but I went for a streamlined interface that got to what most users were after without a lot of clutter. There are currently over 6,000 active users of the app and I've gotten great feedback. Metro also mentions it on their website.