Yesterday’s updates now allow you to back up to an external drive attached to an AirPort Extreme base station, a feature that was previously announced, then yanked, then recently only available through Apple’s Time Capsule. TUAW reported it last night, and now MacWorld and Gizmodo both have the story as well. I set it up last night on my iMac, and the feature works as expected. Attached a drive to your base station, open up the drive in the Finder to mount it, and then go into Time Machine’s preferences and you can select that drive from the list. What I haven’t tested is what will happen when a laptop enters and leaves the network frequently. I’ll be playing with that this weekend.