Alexa did a major update to it's ranking algorithm and source data yesterday. It's supposedly a lot better.

yes ... though it depends who you ask. Many like hacker news rankings went down. Was 14K two days ago... now 77K, while looking down next to my alexa toolbar ranking of this site I have the compete toolbar that says hacker news is ranked 25K. Though compete only measures US traffic, best of my knowledge. Scribd was ranked 900 something now its 500 something. Congrat to Ed K and the Scribd team!