AirFlick is an application that lets you send media to your AppleTV. It uses the AirPlay protocol to send photos, audio and videos to your AppleTV. AirPlay is a new protocol by Apple that lets you share media between Apple devices. AirFlick can only send content to the AppleTV, though.
From the main window, you specify a file path or movie URL for the file that you want to send to the AppleTV or simply drag and drop it onto a drop zone. On the right part of the screen there are two buttons that let you change the type of content that you want to send: Audio and Video, and Images. If you choose images, you can select the image that you want to send, or you can also take a screenshot and send it with a single mouse click, which is pretty cool.
When you are sharing media to the AppleTV using this app, you can control the playback from the application. There are buttons to pause, play and stop the video.
In my testing, I was able to easily send both video and photos to my AppleTV, with absolutely no configuration. Keep in mind that you will only be able to share videos that are supported by the AppleTV. H.264 and MPEG-4 files should play just fine.