I like to provide some statistics about the content of LingQ.
Here are 16 languages which have more than 1000 lessons (a number represents a numer of courses):
English 1000+
French 1000+
Japanese 814
German 643
Spanish 590
Russian 411
Chinese 392
Italian 278
Portuguese 274
Korean 179
Dutch 174
Czech 158
Hebrew 139
Swedish 114
Latin 97
Esperanto 53
PS. Polish and Arabic are comming very soon into the Top 18.