Video Size (Aspect Ratio) for iPod Classic, Nano and Touch?

Please clarify these video size (aspect ratio) settings for videos to be delivered in a podcast formatted for iPods.

1. iPod classic. 4:3
- HD movies and 16:9 videos must be letterboxed in a 4:3 aspect ratio or
- the videos and movies are cropped when viewed on iPod classic

2. iPod Touch and iPod Nano. 16:9
No need for cropping 16:9 aspect ratio movies and videos, will display just fine.

3. What about for other media players like Zune, what aspect ratio should be used? What about for phones?

thanks all.