A shorter version of the Language Construction Kit— the same as the version on zompist.com, plus the Naming Languages chapter from the full Kit.
Create plausible and realistic languages for RPGs, fantasy and science fiction, movies or video games, or international communication... or just learn about how languages work from an unusual, light-hearted perspective. This is the classic set of web pages (suite of web pages?) which has helped a generation of conlangers to understand and create languages, in convenient e-book form.