Yes-oh-yes-oh-yes! You can now finally port your own mobile phone number over to Google Voice. Only catches are that you'll have to pay $20 and have to deal with potential early termination fees being assessed by your current carrier. Updated.
Updated: Some commenters have noticed that this option has disappeared for them, or wasn't available in the first place. TechCrunch spoke with Google, who stated "we're continually testing new features to enhance the user experience. For a limited amount of time, we're making the Google Voice number porting process available to users. We don't have any additional details to share at this time, but plan to offer this feature to all users in the near future."