By default there is no option to upload your videos to YouTube directly from Windows Phone 7 Mango. The sharing interface does not have an option to upload the video to YouTube. But XDA Developers member has added a nice and simple trick which lets you upload videos from Windows phone 7.
1. Open YouTube on your desktop and then log in to your account. Now click on the Upload button and in the upload page, on the right sidebar, you can see an option “YouTube direct Mobile upload”
2. When you click set up, you will be provided with an unique email address which is associated with your account.
3. Add this email address to your contacts list. Now open the video in picture app and then select share. Send this video as an email to the address provided by YouTube.
4. Thats it, your video will be send and you will get the success confirmation.