I recently pre-regristerd for a upcoming mac program called Tubular. It is a YouTube client that allows you to watch your favorite YouTube clips inside of a nice app. Also you can see the featured videos, most recent, most viewed, most discussed, most linked, and top rated.
To pre-regrister I found a link that allowed me to do so for only $9.95 ($19.95 is the release price).
The software allows you to watch YouTube videos in any size you want by simply making the application window larger or smaller.
I understand that any browser is a YouTube client obviously, but this also converts the video for your iPod and imports directly into iTunes. (It will work with your Zune as well).
Here is a screencast that was recently on the Tubular blog:
It is in it’s early beta, but Private Beta 3 was just released to me today. I have to say I am really enjoying it so far. It puts the Apple into YouTube.