Turkopticon helps the people in the 'crowd' of crowdsourcing watch out for each other—because nobody else seems to be.
Almost half of the Mechanical Turk workers who wrote their Bill of Rights demanded protection from employers who take their work without paying. Turkopticon lets you REPORT and AVOID shady employers.
How Turkopticon works:

Turkopticon adds functionality to Amazon Mechanical Turk as you browse for HITs and review status of work you've done. As you browse HITs, Turkopticon places a button next to each requester and highlights requesters for whom there are reviews from other workers. Bad reviews let you avoid shady employers and good reviews help you find fair ones. You can view reports made against requesters with a quick click.
As you review HITs you've completed, are there HITs you weren't fairly paid for? Turkopticon adds a button that lets you review requesters from your "Status Detail" page.
Other Turking resources:
- MTurk Crowd
- MTurk Forum
- MTurk wiki on the MTurk subreddit
- Hide requesters script: for Greasemonkey; for Google Chrome
- List of useful Turking scripts and add-ons from the HITsWorthTurkingFor subreddit
- Turking tips from the MTurk subreddit
"Low cost, high quality" is a myth; you must pay for quality