Earth Minimal language
ebtx.com
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.
Language Creation
pueblacity.com
Describes creating languages as a hobby, includes samples of created languages, with much of the content also available in PDF files. [English/Spanish]
Fictional Linguistics: KICKS Academy Course
feminafelis.tripod.com
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".
Constructed Human Languages
quetzal.com
Comprehensive guide to various invented and artificial languages. Includes links to numerous invented language projects on the web.
Model Languages
langmaker.com
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.
The Language Construction Kit
zompist.com
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.