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

ResourceLoader WM2011.pdf

ResourceLoader
Roan Kattouw and Timo Tijhof @ Wikimania 2011-08-05
Wikimedia Operations Overview
Rob Halsell @ Wikimania 2011 2011-08-05
Editing 2.0: MediaWiki's upcoming visual editor and the future of templates (with notes) @ Wikimania 2011-08-58
OSCON 2011 - ResourceLoader - Trevor and Roan.pdf

Low Hanging Fruit vs. Micro-optimization, Creative Techniques for Loading Web Pages Faster
Trevor Parscal and Roan Kattouw @ OSCON 2011-07-29
Low Hanging Fruit vs. Micro-optimization, Creative Techniques for Loading Web Pages Faster (with notes)
Trevor Parscal and Roan Kattouw @ OSCON 2011-07-29
How to raise millions of dollars using open source software
Arthur Richards @ FOSDEM 2011-07-28
Wikimedia Analytics
Tomasz Finc @ FOSDEM 2011-02-5
Power the world's favorite wiki - Wikipedia @ GNUnify 2011-02-11
Drupal + CiviCRM + Wikimedia Foundation = Awesome
Arthur Richards @ GNUnify 2011-02-11
Hacking Mediawiki: Developing an Extension and Engaging the Community
Arthur Richards @ GNUnify 2011-02-12
Wikimedia Mobile: Past, Present, and future
Tomasz Finc @ GNUnify 2011-02-12
Wikimedia Architecture/Community/The Site Architecture you can edit
Ryan Lane @ SF PHP Meetup 2011-04-06
The Site Architecture You Can Edit
Ryan Lane @ Open Stack Design Summit 2011-04-26
Community Oriented Test and Development
Ryan Lane @ Hack-a-thon Berlin 2011-05-13
In-line editing: a new approach to editing wikis
Jan Paul Posma 7/1/2011

2010

How to be part of the MediaWiki developer community
Ryan Lane @ Kansai Open Forum Conference 2010-11-05 and WCJ2010 2010-11-07
MediaWiki開発者コミュニティに参加するには
Ryan Lane @ Kansai Open Forum Conference 2010-11-05 and WCJ2010 2010-11-07
Wikimedia Architecture
Ryan Lane @ Keynote at Kansai Open Forum Conference 2010-11-05
Wikipediaにおける大規模システムの運用
Ryan Lane @ Keynote at Kansai Open Forum Conference 2010-11-05
Managing content quality in an open collaborative environment
Ariel Glenn @ IFLA Pre-Satellite Conference 8/7/2010
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
Wikipedia's Structured Data Challenge
Erik Möller and Trevor Parscal @ SemTech 2010-06-25
Breaking into Fort Knox: Improving Multimedia Upload Usability
Neil Kandalgaonkar and Guillaume Paumier @ WMF Developer's Workshop 2010-04-15
How Wikimedia is Scaling Open Source Innovation
Eugene Eric Kim, Trevor Parscal and Tomasz Finc @ Xeorx Parc Forum 5/6/2010
Wikimedia Mobile and Offline
Tomasz Finc @ Wikimania Gdansk 2010-07-11
Making things easier to use, one test subject at a time
Trevor Parscal @ WMF Developers' Workshop 2010-04-14

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