It's been far too long since I've open sourced anything, so today I'm happy to open source a small library that I use extremely heavily:
https://github.com/nathanmarz/specter
Specter lets you write code like this:
user> (select [ALL :a even?]
[{:a 1} {:a 2} {:a 4} {:a 3}])
[2 4]
user> (update [(filterer odd?) LAST]
inc
[2 1 3 6 9 4 8])
[2 1 3 6 10 4 8]
user> (select [:a ALL :b ALL odd?]
{:c [1 2 3] :a [{:b [3 4 5]} {:c 1 :b [1 2]}]})
[3 5 1]
More information can be found on the README.