Jagger is going to be one of the “longer” updates, or set of cumulative updates we have seen in a while, with up to 3 stages predicted by some.

Updates happened last week, including PageRank updates. Reports over at Webmaster World are showing signs that the 2nd stage of this update is starting to roll out today (26th Oct). Will there be a 3rd?

Google have taken the unusual step of requesting people report any spam issues you see during or after these updates.

Matt Cutts said : http://www.mattcutts.com/blog/update-jagger-contacting-google/
I especially want to hear about webspam that you see in Google. The best place to do that is to go to http://www.google.com/contact/spamreport.html . In the “Additional details:” section, I would use the keyword “jagger1″ (that’s “jagger” and the number one with no spaces in between).