Android/Chrome: Videostream for Chrome already makes it easy to play any video on your computer or network through your Chromecast. The new Videostream app for Android gives you a remote control to stream movies on your PC, monitor downloads, and control playback without installing a special media server.
The Android app is designed to work alongside the Chrome extension. Once you have it installed and paired with your computer, you can use it as a remote for Videostream, meaning you can have your PC in the study, and then sit down in front of your TV and play videos that are stored locally on your desktop or on your home network right from your phone. You can control playback as well, pause, rewind, adjust the volume -- all the things you would expect to be able to do with a remote control.
The big difference is that you don't have to have your computer with you, and you don't have to let a media server app index your computer or all of your video files just to push a movie you just downloaded to your Chromecast. Plus, since it works anywhere on your home network, you can move the Chromecast from TV to TV in your home, use the Android app as a remote, and just keep your PC in one place.
The Videostream app also allows you to keep tabs on videos and downloads on your PC, so you can play a movie as soon as it finishes downloading. You can browse videos by name (alphabetically), search by keyword, or just look at files in date order. TV series episodes are grouped together so you can even see how much of a specific show you've watched through.
Videostream is free, both for Chrome and Android, and you can try them out at the link below. The app supports subtitles, AVI and MKV files, MP3 streaming and playlists.