retiring Microsoft Points this year.
"Unlike our previous beta programs, sign up is now accessed directly through your Xbox 360 console to streamline the experience," wrote Microsoft's Larry "Major Nelson" Hryb on his site. "Space is limited, so once the spots are filled the beta will be closed to the public."
To sign up, look for the Xbox Beta Program on the home hub of the Xbox dashboard. There will be a non-disclosure agreement to sign and more information should be accessible at the Beta FAQ (not working as of this posting).