This comes right from the "Obvious" department, but I've had various Android devices for over a year now and I just recently discovered how to play videos. Specifically, how to play video without using doubleTwist. This was only a concern for me on my Xoom where doubleTwist was having issues finding the videos I had copied to the device. Apparently everyone else in the world knew this, but you can use the Gallery application for videos. I always thought the Gallery was just for pictures I took. And while I've taken video with my mobile devices before and probably saw "Video" listed in the application, I had assumed it was just for videos taken with the device. I also just never really explored Gallery outside of pictures, and since it also includes videos "midstream" with pictures, I figured that was it. I was surprised to find movies I had copied to the hardware were also available there.

So please tell me I'm not the only one who didn't know this?