The title says it all.
This should use clojure.pprint: http://richhickey.github.com/clojure/clojure.pprint-api.html
A custom printer for Cascalog queries would be extremely powerful. Expanding predicate macros is interesting; more interesting is a printer that names the type of each predicate in a query (filter, aggregator, etc).
This should be really easy now -- in cascalog.logic.parse/parse-subquery, the return of build-query (before it's passed in to build-rule will print out all expanded operations and predicate macros.