The most famous one is the Reuters-21578:

http://www.daviddlewis.com/resources/testcollections/reuters21578/

and the RCV1:

http://trec.nist.gov/data/reuters/reuters.html

There are others in the second link, they are free but you need to fill an agreement form to ask for them.

We used the first data set for several experiments in the attached papers.

Article Minimizer of the Reconstruction Error for multi-class docume...

Conference Paper Document Categorization Based on Minimum Loss of Reconstruct...

Thank you Sir...@Juan Carlos Gomez

http://www.ee.columbia.edu/~stanchen/e6884/labs/lab3/x43.html

http://ssdi.di.fct.unl.pt/~nmm/MyPapers/MB03.pdf