CuteTube is a Youtube client for our Nokia N900, with some very interesting features for browsing Youtube, like the ability to download our favorite videos. Without doubt, the best Youtube application for Maemo.

Browse, search, play and download YouTube videos. Media Player and MPlayer are currently supported for playback, with Media Player giving the best performance in my tests.
Rate videos and view/add comments.
Manage your YouTube account(s). You can add multiple accounts and switch between them dynamically.
Create, edit and view your playlists, subscriptions and favourites.
Create an ‘on the go’ playback queue, which can also be saved as a YouTube playlist.
Full auto-rotation support in all windows and dialogs.
Also you can share videos on your facebook or twitter account

CuteTube is available in the Extras-Devel repository.