The Language Construction Kit (zompist.com)

I had a side project like this: the idea was to create a website where people could select the phonemes they want, the syllable structure, a base vocabulary (Latin, Chinese, etc.) on which certain transformations would me made, some grammatical property and the website would then generate a tutorial to learn the language and basic automated translation tool. For each step, there would have been some short explanations about the relevant linguistic concepts at hand.

I stopped at the phoneme selection page and didn't make any release but from time to time I'm thinking about actually finishing (and open-sourcing) that single page.