Head over to Skillcrush for a roundup of visual programming environments that are geared toward kids, but from my experience they can be fun and informative for adults, too!
I have used Scratch to teach middle school and high school students programming concepts, and I have used Alice to teach educators interesting ways to bring technology to the classroom. The materials we used to teach the students and educators were developed by groups at my school, Lamar University.
I’m not familiar with the other programs mentioned (Google Blockly, Microsoft’s Kodu, Hopscotch, Mozilla’s Hackasaurus and Thimble), but I will definitely look into them. Mozilla also encouraging people to host “Summer Code Parties” to get groups of varying sizes together to learn coding or create content for the web.