Apparently your excitement for this fall's Xbox 360 Dashboard update beta was so great that Microsoft caved to demand and reopened its gates for 500,000 more participants. That's at least according to an Engadget tipster, though Microsoft's Major Nelson is only saying that the program is open to more testers this time than in its first round.
Like in the previous round, once the signups are closed, they're closed, so get your name in while the getting's good! If accepted, you'll get access to Internet Explorer's Xbox 360 version, enhanced search functionality, and bragging rights that you were in the beta "before it was cool." Full beta features are below the break.