I am posting some of the things I found useful. Primarily for my own memory, as I forget how I did something later.
Youtube on WP7: Sometimes when you try to open a hyperlink to a youtube video which someone sent to you via e-mail and you try to open it in the Windows Phone, it might not be able to play it. This is primarily because you are trying to open the desktop version of the hyperlink.
To view such youtube videos on your WP7 device, which you sometimes receive in your e-mail, but which has the hyperlink to the desktop version such as follows: Double-click on the URL in your e-mail and as it opens in the browser address bar, change the WWW in your URL to M.
http://www.youtube.com/watch?v=f1sN2Q6ded8, replace the “WWW” with “m” for mobile and it should open up. That is instead of http:/www.youtube.com replace the URL in your IE browser address bar to http://m.youtube.com/blabla and it should open up.
Alternativel;y there is also a setting in your WP7 device for the Internet explorer. Go to Settings->Applications->Internet Explorer->Website Preference and set it to “Mobile Version”.
OfficeLive on WP7:
It is likely to see all your OneNotes under unfiled section in the WP7 device. But once you sync up, and go to http://office.live.com on your WP7 device or on the desktop browser and sync back to your PC you should see them in the specific notes section where you expect them to be.