DIY gear successfully made and used?

I am looking around for a DIY project to work on over Christmas.

I have seen lots of suggestions at DIY Photography and a few at The Strobist.

(In particular, there are lots of light modifiers and different ways to mount lights - which is great, but I'm after more too).

I feel sure that this community can come up with some cracking ideas too, and I would love to hear about any projects you have successfully(!) executed to build your own photo gear.

If possibly, please include links, photos, instructions, etc. so that others (including me) can follow in your DIY footsteps!

Edit

I meant to flag this community wiki, but I can't see how to do it. Am I going mad? blind? Can someone else flag it? Thanks.

Answer

I built a gel holder/mount for my nikon flash.

First, I went to my photo store and asked for the sample kit of gel for photo/flash. It sells for about 3$ and it has a hundreds of colors and neutral density papers (including CTO).

I used card board to build the mount. I simply slide it over the flash head and insert the gel into a small slot.

Here are examples :

Also, not related to photo, but more video: I build a steadycam to have more stable video when moving. Search in google for : diy steadicam