TubeQueue

TubeQueue is a .NET based YouTube video downloader and video converter. It uses ffmpeg for video and audio conversion. It is unique in that it uses the concept of video conversion queuing, which essentially enables you to apply any combination of video conversions to any combination of videos downloads directly from YouTube. The built-in search allows for batch searching of playlists, subscriptions, favorites, uploads of a particular user, and general videos (example usage: downloading a 10-part video series in batch) and the traditional YouTube search page supports browsing YouTube to find the videos you want (like many other YouTube apps).

TubeQueue supports converting YouTube videos to AVI, MP4 for iPod 5G, MP4 for iPod Touch/iPhone, mpeg, mov, FLV, and many more file types. You can also tweak the default ffmpeg settings built into the program and modify them to your specific desires, and then save the resulting tweaked conversion for later use.