TubeMate

[TubeMate - The fastest and most famous YouTube downloader]
TubeMate allows you to download YouTube videos so you can watch them offline!
* Fast download mode(with multiple connections for a download)
* Multiple download resolution options
* Background, multi-download
* Resume downloading
* Convert to MP3 (powered by MP3 Media Converter)
* YouTube search and related videos suggestions
TubeMate YouTube Downloader enables you to quickly access, search, share, and download YouTube videos.

Downloaded videos are stored by default onto your smartphone, but you can also download them directly onto your SD card. Definitively TubeMate 3 is a downloader tool that's really easy to use and has the added appeal of allowing you to download any video file off of YouTube within seconds. This third version of the app also has a very elegant interface that's a major improvement on earlier versions. 

Because downloading always happens in the background, you can go on watching YouTube, surfing the Internet, tweeting, and listening to your music as you download.