Penn State has released it's report into the Michael Mann investigation. Here is a link to the report, the statement of it's conclusion, and a snippet about the process.

Conclusion of the Investigatory Committee as to whether research misconduct occurred:

The Investigatory Committee, after careful review of all available evidence, determined that there is no substance to the allegation against Dr. Michael E. Mann, Professor, Department of Meteorology, The Pennsylvania State University.

More specifically, the Investigatory Committee determined that Dr. Michael E. Mann did not engage in, nor did he participate in, directly or indirectly, any actions that seriously deviated from accepted practices within the academic community for proposing, conducting, or reporting research, or other scholarly activities.

The decision of the Investigatory Committee was unanimous.

http://live.psu.edu/fullimg/userpics/10026/Final_Investigation_Report.pdf
(The critical points in this report have been helpfully marked out with yellow backgrounds - look for the yellow to extract the most important items.)

From November 30 to December 14,2009, staff in the Office for Research Protections culled through the 1073 files that contained emails or email strings that were purloined from a server at the University of East Anglia. A subset of the files containing emails or email strings was reviewed. This subset of files included emails that were sent by Dr. Mann, were sent to Dr. Mann, were copied to Dr. Mann, or discussed Dr. Mann (but were neither addressed nor copied to him). In summary, the following were found: 

       206 files that contained emails or email strings that contained messageltext from Dr. Mann somewhere in the chain;
       91 files that contained emails or emails strings that were received by Dr. Mann, but in which he did not participate; and
      79 files that contained emails or email strings that dealt with Dr. Mann, his work or publications but that he neither authored nor was listed as copied.

From among these 376 files, the Inquiry Committee focused on 47 files that contained emails or email strings that were deemed relevant. On December 17, 2009, the Inquiry Committee (Pell, Scaroni, Yekel), Dr. Brune and Dr. Foley met to review the emails, the RA-1O inquiry process, and their respective activities. It was agreed that these individuals would meet again in early January and that they would use the time until that meeting to review the relevant information, including the above mentioned e-mails, journal articles, OP-ED columns, newspaper and magazine articles, the National Academy of Sciences report entitled "Surface Temperature Reconstructions for the Last 2,000 Years," ISBN: 0-309-66144-7 and various blogs on the internet.