This is a more advanced modification that requires disassembling part of the camera and doing some soldering to switch out a capacitor, but the instructions are clear and have good photos of each step.
Check it out at Holgablog

"g." on Polanoid figured out how to make his own Polaroid Chocolate/Sepia peel-apart film! Apparently you need a B&W positive and a color negative… check out these instructions and example shot, very cool!

Flickr member Dark Orange says:

Can’t buy the film you want any more? Just make the stuff!
In this set you will find random photos and information on a project a friend has undertaken – a machine to make his own camera film.
Plastic and goop go in one end, and camera film comes out the other end. [...]

Check out Rob’s DIY 555-based remote timer for Canon SLRs! He says:

Canon makes a SLR camera remote timer that sells for a couple hundred dollars. Using inspiration from various web sites I built one for myself using about $15 worth of parts from RadioShack.
First, it is a simple wired camera remote control. Just plug the [...]

Instructables member Tool Using Animal writes:

For years I’ve wanted to mess around with UV photography. Unfortunately, all the websites on DIY UV seem to assume an infinite amount of money and access to specialized equipment on my part. There are two things that I don’t like, when someone tells me I HAVE to spend a [...]

Bf5man writes: "A useful trick to repair or to do a mockup of a plastic part, is to disolve ABS shavings in acetone, it forms a glue that can be used to repair plastic stuff, or if thicker, can be used to mold things. Here’s an exemple of what can be accomplished with this method."

Sounds [...]

Science photographer Ted Kinsman wrote this piece on building and calibrating a photodiode-based light meter:

Being in the professional science photography business, I often get asked to photograph the strangest stuff using some very weird lens combinations. Lately, I was asked to take some motion pictures of "microscopic animals". So I set up the microscope and [...]

f295 member greyhoundman has posted instructions for how to build an ultra-cheap filter holder for large format lenses:

Ok, I know someone probably sells an adapter for holding filters on a large LF lens. But, not around here, and I like to see what I’m buying.
So again I decided to build what I need.
I used, 1 [...]

Flickr member idiot king writes, "”I just made a light tent that’s a little larger than this one (it’s 4′x3′) with a roll of paper for the backdrop and bedsheets as diffusers. I think it cost, in total, about $30 for wood and paper. This will come in real handy for portfolio shots!"
Via MAKE Blog

"Here Brian shows how to build a homemade cheap flash bouncer. The flash bouncer can be used to increase the size of a hot-shoe flash. The bouncer is great and very easy to build. An alternative to the bouncer is the home made softbox. Another option for building this homemade flash bouncer is to use [...]