Desiree Dolron is a documentary photographer who has travelled to India, the Philippines, Pakistan and Morocco to photograph religion and death in these cultures. Also see her Cuba portrait series, which is especially lovely (via Scene 360).
Tips and tricks for modifying and improving your Holga.
The definitive Holga modification and disassembly resource page, including how to fix light leakage.
Toy Camera features a special Holga primer, as well as tips on modifying the lens and which parts to tape up.
Holga isn't just medium format. They even make a 35mm version of their camera.