Wikimedia Downloads: Database tables as sql.gz and content as XML files

See the list of database backup dumps.
Also see daily dumps of additions/changes to content (Experimental!)
Historical material only: archives of sql/XML dumps for previous years starting from 2001

Other content

Wikidata JSON dumps
Pagecount data collected by Domas Mituzas
Pagecount/projectcount data derived by Erik Zachte from Domas Mituzas' archives
Pagecount/projectcount data including mobile/zero sites
Request counts for the upload domain (pictures, movies, audio files)
Static dumps of wiki projects in OpenZim format (mirrored from Kiwix)
WMF Survey data
Picture of the Year Zip or GZ files
The top 6 submissions of the WikiChallenge data competition, contains source and data
April 2011 English language Wikipedia revisions as additions/removals to the previous text
1911 Edition of the Encyclopedia Britannica, scanned as tiff files
User signup data for the Wikipedia Education Program