There are various presentations available about wikipedia architecture and its sub projects on the web. Here are a handful of the ones that were scattered through the web.

2011

Wikimedia Analytics
Tomasz Finc @ FOSDEM 2011 2/5/2011
Power the world's favorite wiki - Wikipedia @ GNUnify 2011 2/11/21011
Drupal + CiviCRM + Wikimedia Foundation = Awesome
Arthur Richards @ GNUnify 2011 2/11/2011
Hacking Mediawiki: Developing an Extension and Engaging the Community
Arthur Richards @ GNUnify 2011 2/12/2011
Wikimedia Mobile: Past, Present, and future
Tomasz Finc @ GNUnify 2011 2/12/2011

2010

Making things easier to use, one test subject at a time
Trevor Parscal @ WMF Developers' Workshop 4/14/2010
Breaking into Fort Knox: Improving Multimedia Upload Usability
Neil Kandalgaonkar and Guillaume Paumier @ WMF Developer's Workshop 4/15/2010
How Wikimedia is Scaling Open Source Innovation
Eugene Eric Kim, Trevor Parscal and Tomasz Finc @ Xeorx Parc Forum 5/6/2010
Wikipedia's Structured Data Challenge
Erik Möller and Trevor Parscal @ SemTech 6/25/2010
Wikimedia Mobile and Offline
Tomasz Finc @ Wikimania Gdansk 7/11/2010
Why your extension will not be enabled on Wikimedia wikis in its current state and what you can do about it; security, scalability and performance for extension developers
Roan Kattouw @ Wikimania Gdansk 7/11/2010
Managing content quality in an open collaborative environment
Ariel Glenn @ IFLA Pre-Satellite Conference 8/7/2010
Wikimedia Architecture
Ryan Lane @ Keynote at Kansai Open Forum Conference 11/5/10
Wikipediaにおける大規模システムの運用
Ryan Lane @ Keynote at Kansai Open Forum Conference 11/5/10
How to be part of the MediaWiki developer community
Ryan Lane @ Kansai Open Forum Conference 11/5/10 and WCJ2010 11/7/10
MediaWiki開発者コミュニティに参加するには
Ryan Lane @ Kansai Open Forum Conference 11/5/10 and WCJ2010 11/7/10

2009

Using CiviCRM at Wikimedia
Tomasz Finc @ CiviCRM Meetup/Wikimedia
Wikimedia Technical and Operational Infrastructure
Rob Halsell @ Wikimania 2009 Video
Wikimedia Search
Robert Stojnic @ Wikimania 2009
Codathon round-up
Brion Vibber @ Wikimania 2009
XML Data Snapshots
Tomasz Finc @ Wikimania 2009