When I was looking through the new edition of The Filmmaker's Handbook, I noticed a lot of little changes and additions. An example: In a list of equipment to bring to the set, in the lighting category I noticed one addition: "dimmer boxes." I can't argue with that -- dimmer boxes help one light with finesse, and they're fairly easy to come by. I went to the trouble of making a couple dimmers (aka "hand squeezers") myself about a year and a half ago. I made a couple of 600 watt boxes, as well as a 1000 watt box. The supplies I got from the local home improvement store, though I remember that the 1000w dimmer was not widely available. If I remember correctly, I built all three dimmer for about $100 in supplies. They would have been cheaper, but the 1000w dimmer was considerably more expensive than the 600w.
In retrospect, instead of making those boxes, I would have been better off simply purchasing one of the many dimmer boxes or router speed controls (which can be used as a dimmer box) that are commercially available. They're cheaper, they're probably more reliable than anything I could build, and the heavy duty router speed controls can handle more power than the ones I built. Plus, the router speed controls have a safety fuse, which my self-built dimmers lack.
Shopping for some last week, I ran across lots of varieties. Here are some:
Ikea Dimma - 300 Watts and under - $7.95 Note: Not useful for most motion picture lights, but if you just need something for practicals, these are nice and cheap.
Smith Victor - DC-1 Dimmer Control - 600 Watts and under - $23.95
Router Speed Controls:
Harbor Freight Tools - 15 Amps and lower - $19.99
MLCS Router Speed Control - 15 Amps and lower - $20.95 and $28.95, respectively, for the "home" and "industrial/commercial" use boxes
Grizzly G3555 Router Speed Control - 20 Amps and lower - $31.50
Rockler Router Speed Control - 20 Amps and lower - $39.99
If, however, you wish to build your own, you can find instructions in Blain Brown's Motion Picture and Video Lighting, 2nd Edition (p. 241) and, of course, there are plans aplenty on the 'net.