I've tried posting on the blog under the name "Gulag Picture Radio" BTW, and while I'm all registered and everything I don't see any of my posts anywhere. Just thought I'd mention that.
Anybody else having trouble posting comments? I'll check on it... -W
A few items that I've used in front of the camera are as follows:
Anamorphic lens taken from a WWII gun camera (?). It weighs around 20 pounds and has a mount unlike anything I've ever seen - it's about 6-8" across. Needless to say I never actually mounted it to the camera, instead holding it. I also seem to remember devising some sort of mount on a mic stand. I've used it with several video cameras (Canon L-1 and XL-1 come to mind) and with a Bolex 16mm camera.
Fresnel magnifying sheet originally manufactured as a cheap magnifying glass for older folks. Because it is thin plastic and flexible, you can get a lot of cool distortions that way. I've also seen similar flexi sheets with a bunch of little miniature fresnel patterns on them. They are sometimes used as privacy screens that you paste to your bathroom windows to let light in, but not let anyone see in.
Thin (but stiff) mylar squares - often used as mirrors in kids toys or books. Mount this in front of your camera at a 45 degree angle, then shoot your subject with the camera pointed sideways in relation to them. Flex the mirror for weird effects, remembering to flip the picture orientation in your editing software. The BBC used to use this effect for Doctor Who for when the Ice Warriors shot anyone. They used something called "Mirrorlon" which I would expect to be much thinner than the mirror I'm talking about which would give you some nice ripply distortion.
I've also used a lot of still photography filters with video cameras. Here in Chicago there are massive photography swap meets where you can get tons of special effects filters for next to nothing. Many of them can be useful for video. I've used a star filter, fly's eye filter (image in middle surrounded by 5 identical images, and filter can rotate - great for 60's pop singer look), polarizing filter (great for cutting glare when shooting through a window, or for making a car look less scratched up), center focus, some gradiated filters for dramatic skies...
The problem is that with my current video cam (the Canon XL-1) the lens is so massive, it's so hard to find filters to fit it at these swap meets. Common filters for still photography are 45-55mm (probably other sizes too), and the XL-1 clocks in at a massive 72mm. You can get adapter step-down rings to compensate, then zoom in a little to avoid vignetting.
There are also some great gadgets that I've used with old film cameras in front of the lens that aren't filters. My Bolex has had an iris attachment (for transition effects), a clock work device for a variety of animated wipes, titling rigs, and my personal favorite... a 3D lens set for shooting 3D films. Before you ask, yes I've shot some 3D footage, but I'm missing one important part of the projector arrangement to see if my experiment worked. :)