[puredanger]

And REBL http://rebl.cognitect.com/download.html

[stuarthalloway]

And Fressian https://github.com/Datomic/fressian/wiki

[puredanger]

And core.async, bringing go blocks, channels, and parking semantics to Clojure

https://github.com/clojure/core.async/

[gleenn]

I think REBL is actually more of Stuart Holloway's baby, isn't it? They're close, so maybe this isn't so clear.