Massive Voodoo has an interesting article on which light to use for painting. I used a halogen light for many years,
Creative Twilight has a blog post on painting freehand details on miniatures, such as logos on crates and the like. It fits in well with my thesis that painting miniatures is a skill that can be acquired, not a talent.
Cool-Mini-Or-Not has a good article with pictures on painting non European skin tones. There are photos of the various peoples, along with virtual paint chips and a discussion of how to replicate those tones.
When you’re painting a house, it’s said that the preparation is most of the work — and that poor preparation will always result in a poor outcome. I think the same may apply — to some extent — to miniatures. A poor undercoat ruins your figure before you even start. Too much primer, too little, too slick, too grainy. There are a million ways to ruin a figure. Here’s an article on the subject of undercoats.
Grey Goat studios has this tutorial on airbrushing your wargaming miniatures.