To submit your app to Marketplace for distribution, you will need an App Hub Account. Open one at: http://create.msdn.com
Opening an account is also necessary to developer unlock your Windows Phone 7 hardware.
Tip: Make sure you use an international credit card if opening an account outside of the US.
Tip: If you will use this account for a company, do not use a personal Windows Live ID when creating the account. You don’t want to mix your personal account details with your company’s and after you create the account, you can’t change the Windows Live ID.
For a guide of the Windows Phone 7 registration process, see here.
For a guide of the Windows Phone 7 Marketplace application submission process, see here.
To help teams track their progress in meeting the Windows Phone 7 certification requirements, I’ve created the following guide. I have used this myself when reviewing partners applications prior to submitting to Marketplace. Please see the instructions on the first tab.