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It's pretty brand new, so I don't think there are any "real" projects using it yet. But you can check out this example repo from David Nolen (the blog posts author) for some more examples.

https://github.com/swannodette/async-tests

This is an example of Peter Norvig's spellchecker written with core.async by Stuart Sierra (@stuartsierra): https://gist.github.com/stuartsierra/5954022

This is an example of Rock Paper Scissors by Alex Miller (@puredanger): http://tech.puredanger.com/2013/07/10/rps-core-async/

Microsoft Rx -style operations https://groups.google.com/forum/#!topic/clojure/L4nEVho555k