After beta testing for years, it has finally become widely available for most U.S. passports to be renewed online.
Direct link to renew your passport online
There are so many advantages to renewing online:
No need to go to CVS to get get a printed photo; just have a friend to a picture on your phone and upload the image
Saving on the cost of the registered mailer; the online process should also shave a couple of days off the time it takes to process
Pay with a credit card; no need to send in physical check
Etc.