This article is from the Artificial languages FAQ, by Rick Harrison firstname.lastname@example.org with numerous contributions by others.
From time to time periodicals have been devoted to artificial
languages. International Language Review and Journal of Planned
Languages covered a variety of language projects during their
lifespans. (JPL is on hiatus now but might attempt a comeback
someday.) Periodicals devoted to particular auxiliary language
projects (e.g. Rund um die Welt and Cosmoglotta) sometimes
covered other language proposals, or so I've been told -- they
are not easy to find.
A bibliography of relevant books is at