I don't know how many phone calls my house gets in a day that say "name unavailable" on the caller ID. Have you ever wondered who's calling? Tim O'Reilly pointed at whocalled.us yesterday. This great little Web application lets you enter the phone number and see comments from other people who've received calls from that number. A clever anti-spam hack and a good example of smartmobs in action.
Must read: Windows 8.1 update leaks to the web early