When I was a child, I wanted to learn Chinese. Unfortunately, at that time in my country finding a handbook of Chinese was not easy. There were no such books in the bookshops. I lost that time because I did not have access to the instruction materials.
The situation in my country has changed now. It is no longer a problem to buy a handbook of Chinese. And even if there were no hard-copy books in the local shops, I could order that book in some internet bookshop abroad.
Unfortunately, not everyone can do that so easily. Not everyone can pay Amazon prices, not everyone has a card to pay in Internet. And even those that do, may find out that it is not always easy to buy a good, up to date book about some less popular languages. If you do not believe, try to buy a good handbook of Xibo or Tangut.
I can see that lots of people are interested in languages. There are several web sites addressing this community, but usually they do not offer much. A forum, simetimes some low quality instructional content, sometimes a paid service to find you a language exchange partner. The most informative, content rich sites that I saw, are libraries of illegaly digitized commercial handbooks, dictionaries and grammar.
I believe that collaboration on open source rules can lead to better language handbooks than what is currently available on the net, in the same way as it gave us better OS (Linux) and better encyclopaedia (Wikipedia).
This project needs help from various people. We need computer specialists to help with creating TeX macros, linguists to make our guidelines and mentor the development of the books, artists to create the graphics, publishers to create the standard look for our books, typographers to create non-existant fonts etc. etc. And, of course, people that will actually write those dialogs and texts, compile vocabularies, write exercises and explanations of grammar, provide civilization notes.
If you want to help, please join NetLingua.