http://www.clickworker.com is based in Europe, with European workers and has a good reputation.

As others are suggesting, Crowdflower works, and works well, with an excellent API. Also they are just good people. (They use an assortment of workforces)

For smaller jobs self service jobs like the one described in this article SmartSheet UI is amazing. http://www.smartsheet.com/ (MTurk based)

And if you need bigger stuff (or text oriented stuff), with some consulting you can contact me, or my company http://castingwords.com (MTurk based)