Question: I had some workers work on a few HIT's and their results were quite good. I have their worker ID's but I dont know how to contact the workers though the MTurk interface.
Any Suggestions?
Answer: Assuming you haven't deleted the batch or HIT: Go into "Manage", "Manage HITs individually", and then find a HIT that the worker has done, and go into that HIT, go to the approved (or rejected) tab, and find the worker id, click that there is an option for "Send an e-mail message".
Otherwise you will need to use their API directly.
If the worker no longer appears in the "Manage HITS individually" area, you can also use the online "Mechanical Turk Email Sender" here:
http://www.siteapproach.com/mturk-email-sender.php