The Holga was designed to be a cheaply mass-produced, functioning camera, and that is exactly what it is. It uses 120 film, which makes it, in my opinion, the best "bang for the buck" in medium format cameras. You can get a new one on eBay for $20, but then you have to pay $14 shipping. I actually saved a little over a buck by paying $30 plus tax at a local camera store (Camera Co-op), and it was nice not having to wait for delivery. At that price, you can modify your camera yourself, without having to worry about hurting an expensive piece of photographic equipment. Plus, they still make them, so you don't have to ruin a collector's item like the Diana. (Not that the Diana is so rare. They made tons of them.) Go ahead and boil the plastic lens for added effect. Who cares? The whole camera costs less than some of my fellow photographers pay for lens caps. (And the Holga comes with a free one included at that price!) Two modifications that I have not done yet, but I feel are important are: the aperture modification (1, 2) and taping the film counter window.
If you are looking for links to other Holga sites, start here:
Holga Cameras and Experimental Photography
It starts with some info about the camera and then lists several other sites at the bottom.