The blog of Jakub Jilemnicky , a marvellous resource for a list of Haworthia species, locations, and photos of plants in habitat:

All you wanted to know about Haworthia, Gasteria & Astroloba

Gerhard Marx’s blog, excellent information and photos and background of some of his amazing hybrids, just read through the entire site:

The Haworthia Society, every haworthia enthusiast should be a member. Also give access to some nice and affordable seeds from time to time:

The Haworthia Society

Some Facebook groups:

Marc Batchelor’s Facebook group, if you are growing haworthia from seed, you should be a member:

The International Haworthia Study Group