Constructed Human Languages - A guide to various invented and artificial languages. Includes links to numerous invented language projects on the web.
Earth Minimal language - Are you feeling terse today? It may be hard to get any more precise than in an "Earth Minimal Language" expression. Check out this incredible language from EBTX.
Fictional Linguistics: KICKS Academy Course - Online free course about creating languages, hosted at the KICKS Academy of the SciFiVine. Members of the SciFiVine may participate after a free registration in the class project for an invented language called "Trans-Galactic Lingo". KICKS stands for "Kenobi Intergalactic Council of Kindred Spirits".
The Language Construction Kit - Intended for anyone who wants to create artificial languages -- for a fantasy or an alien world, as a hobby, as an interlanguage. It presents linguistically sound methods for creating naturalistic languages -- which can be reversed to create non-naturalistic languages.
Model Languages - Free open source LangMaker software for Windows to help design consistent languages for all kinds of settings. Build a vocabulary from scratch or extrapolate from real examples.