The OS FLV Player is an Open Source, embedable player for Flash native video files. The player provides a large amount of options that can be changed in the embed code. Also provided are a code generator written in javascript, a library of PHP functions and, of course, fully open source code!

Website: http://www.osflv.com

With over one million active users, the JW Player™ is the Internet’s most popular open source video player. It supports playback of any format the Adobe Flash Player can handle (FLV, MP4, MP3, AAC, JPG, PNG and GIF) and now supports HTML5 too. Additionally, the JW Player™ supports RTMP, HTTP, live streaming, various playlists formats, a wide range of settings and an extensive JavaScript API. The JW Player’s™ skinning functionality allows you to completely customize its look and its plugin architecture allows you to easily extend the player’s functionality.

Website: http://www.longtailvideo.com/