Marketplace
I found this as a good app for downloading videos and it has a good reviews too
I dont know how long will be for free
there is the description of the app:
Download free and legal streaming videos from a variety of tubes and video sites to your iPhone, iPod Touch and iPad! Keep your favorite videos always at hand and watch them whenever and wherever you like.
App Features:
★ Fully integrated web browser
★ Smart download manager, supporting most of tubes and video sites (such as YouTube, VEVO, Dailymotion and more)
★ Download as many videos as you want
★ Download in background mode
★ Download videos larger 20MB over 3G
★ Play videos directly from the application
★ Play videos in background mode
★ Built-in file manager supporting thumbnails, sorting
★ Manage your own playlists
★ Share Files on iTunes
★ Save videos to camera roll
★ Buy once and use Free Video Downloader Plus Plus on all your i-Devices
Free Video Downloader Plus Plus is constantly updated with new features. If there is anything you would like to see in the application just drop us an email through the “Send Suggestion” link in app’s “Settings” and we will do our best to add this feature in our next app update.
Legal Notice:
If you download a copy of video content, you must retain all copyrights and other proprietary notices contained in or on such content and material. Any material downloaded through this app is accessed and viewed at your own discretion and risk. You will be solely responsible for and hereby waive any and all claims from Free Video Downloader developers.
Looks good! Another good one is TubeBox, which was free a few weeks back