Here are a few of my favorite crowdsourcing links. They're not all directly related to Mechanical Turk, but you may find them interesting.

Research on crowdsourcing complex tasks, such as writing articles (open source):

http://smus.com/crowdforge

A company that adds an automated quality layer and/or automated peer review layer:

http://www.crowdflower.com

Crowdsourced translation:

http://www.mygengo.com

Audio transcription through MTurk:

http://www.castingwords.com

Crowdsourcing scientific research:

http://www.hypios.com/