TubeMate is a good app for Android device available in Android Market. It allows a user to download various types of resolution for the video file available on YouTube.
How to Install TubeMate on Android Device?
a. Go to Settings > Security > Device Management and check the box to “Unknown Sources”
This will allow a user to install third party apps for your device.
b. Download TubeMate app from your Android Market.
Click on tubemate apk file and start the installation by clicking “Install”.
Run the App, select video to play, on bottom click Green Arrow, a window will open saying “Download”. Click it, select file type you want to download.
Video must now be available in your storage folder!