MxTube is a fantastic new native application for jailbroken iPhones. If you're one of the lucky few with a jailbroken handset and the installer app, you'll find MxTube in the recent packages section as of last night. The app is fairly similar to the iPhone's native YouTubevideo viewer with the added benefit of being able to download entire clips and save them to your phone's memory for offline viewing.
Downloaded videos don't show up to those in your regular video library, and won't sync up into iTunes the next time you plug in your phone, but they can be deleted one at a time just like regular video files in case you start running short on space.
The app has a search tool that lets you hunt for videos, and each one has the option to download the higher or lower quality version in case you feel like trying to save space. Downloads can be stacked up, although in its current release, having more than one video in the download queue seems to crash it.
Speaking of crashes, the app is has a handful of bugs that make it a little volatile, including one that doesn't let you exit playing videos unless you hit the home button. Otherwise it's a fantastic tool for grabbing a ton of free video content without having to deal with the molasseslike speeds of EDGE or third-party ripping tools that require syncing with iTunes to transfer content.
I've embedded a demo from the creator of the app after the break.