Paul C. Buff the company that makes the very highly praised Alien Bees lighting systems has some really informative tutorials and articles in the company's forums. The most interesting and useful sections look to be Studio Flash Explained and Sample Lighting Setups which include very useful text descriptions and diagrams of various lighting setups and situations. If you're interested in studio lighting you could do worse than spending some times with these articles.

Photography enthusiast Nick Pagazani was hindered by the range and fixed location of his camera's flash. Since his camera has no connector for an external flash, he needed a light-activated slave trigger to fire a remote strobe. It had to ignore the pre-flashes used for red-eye correction and fire only on the main flash. His solution: Use a microcontroller to count pulses from a phototransistor and trigger the strobe at a switch-selectable count.

Case #96: Nick Has an Illuminating Flashback at Design News

I think this is a little too complex for most people (heck, it's way too geeky for me) but it's a neat project to look at.

If you're in the early stages of your relationship with artificial light and light modifiers the Light Shape Comparison offered by Bron Elektronic has a ton of visual comparisons between different lighting equipment. Obviously they're only showing equipment they manufacture but the basic comparisons are extremely helpful. Side by side identical shots show you what a portrait taken with a conical snoot looks like compared to one taken with a ringflash or a reflector or a silver umbrella, or any of several other lighting options.

Via Strobist

A Danish (I think Danish anyway) has put together a great step by step tutorial about how he setup the background and lighting for a Christmas card family portrait. Called The Making of a Christmas Card it details building a light panel, positioning two flash units, and incorporating a gobo. It's tutorials like this that make lighting so much easier to understand for photographers looking to take the next step up from using only available light and on on-camera flash. It's definitely worth looking at if you're interested in portrait lighting.