Here is our list of subject wikis:
|Wiki||Main topic||Page count (lower bound)||Creation month||State of development||Content being added?||Error log||Pageview count (2015) (Google Analytics)|
|Groupprops||Group theory||7200||December 2006||beta||Occasionally||here||881,735|
|Topospaces||Topology (point set, algebraic)||600||May 2007||alpha||No||here||96,944|
|Commalg||Commutative algebra||400||January 2007||alpha||No||Not yet||12,309|
|Diffgeom||Differential geometry||400||February 2007||alpha||No||Not yet||4,317|
|Number||Number theory||200||March 2009||alpha||No||Not yet||5,271|
|Market||Economic theory of markets, choices, and prices||100||January 2009||alpha||Occasionally||here||209,792|
|Mech||Classical mechanics||50||January 2009||alpha||No||here||53,526|
|Cellbio||Cellbio||30||September 2011||alpha||No||Not yet||843|
|Learning||Learning, teaching, and mastery||25||September 2013||alpha||Occasionally||Not yet||873|
NOTE: The creation month need not coincide with the month of MediaWiki installation. In cases where the wiki was ported from elsewhere, the creation month may be earlier; in other cases, it may be later if the first edits happened long after installation.
Pageview count note: Estimates are based on Google Analytics data, not based on MediaWiki internal logs, which record about 2-3X the pageviews recorded by Google Analytics.
You can access the history of subject wikis here.