http://www.mluvtecesky.netThis one looks similar to
http://slovake.euDuolingo Czech looks really good. It might be better than some of their courses for the bigger languages, the team seems to have made a very good job, taking their time has paid off. In this case, the low popularity of Czech might be an advantage, as there is little motivation for Duolingo to dumb it down to get more public (I've heard they've been changing the German course
).
http://www.mozaika.eu/category/zdarma-cviceni-online/ some graded blog articles
http://www.studyczech.cz/cs/zdroje-pro-studium-cestiny/here is an interesting list, including sites with video and audio
http://www.mojecestina.cz/this is for native children, but I think some of the exercises may be useful to foreign learners too.
http://slovnik.seznam.cz is one of the good choices for an online dictionary
http://forvo.com (I might be a Captain Obvious here)
public domain ebooks (Gutenberg would make you think there is nothing
):
http://www.sesity.net/elektronicka-knihovna.php these are books that tend to be obligatory in schools, mostare public domain. I am not sure about a few, but most clearly are. You can start with Malý princ (Le petit prince), or something else you already know. Out of the originally Czech books here, I recommend Čapek and Poláček as very pleasant reads, even though not necessarily the easiest. Nothing is probably easier there than Malý princ, a very common choice of learners of various languages.
http://www.databook.cz/e-knihy-zdarmamany more books, not just the obvious school choices, including stuff like the Arthur Conan Doyle translations. There are also contemporary authors, who agreed to make their works available for free, but I don't know whether they are good.
Warning:don't use this
http://www.allysatis.org/ficheeleve/ele ... langaff=73Google offered it, there is not much to do, but the little there is includes tons of mistakes. Exactly the kind of resource I warned against on the free challenge page, the creators count on people not finding out.