You could install mytube.
The problem is that it doesn't work as is. It's possible to fix it but it's not that easy.
Look here:
http://talk.maemo.org/showthread.php...369#post914369
and the rest of the thread

(specifically here:
http://talk.maemo.org/showthread.php...661#post916661
and here:
http://talk.maemo.org/showthread.php...872#post916872
)