Red-cooking (紅燒/hóng shāo) is a style of Chinese cooking often used for pork (肉/ròu). The red colour comes from a combination of caramelised sugar and soy sauce, and additional flavour is imparted by Shàoxīng wine and star anise. Optional extra ingredients include garlic, fresh ginger, and cassia or cinnamon bark. One of the most common cuts used is pork belly, cut into chunks but with the skin and fat retained to melt into a delicious tenderness as the meat braises.
I've seen 紅燒肉 on lots of Chinese menus here in London; the photo above is of a version I ate at Dragon Inn on the Old Kent Road. It's not hard to make at home, though. I have a couple of recipes to suggest, each with its own characteristics, and the background information at both links is also well worth reading. The first is an adaptation of a recipe by Fuchsia Dunlop, and the second is a recipe from the Red Cook blog (written by a Singapore-born blogger who likes red-cooked pork so much he named his blog after it). (Edit, June 2011: Kian at Red Cook has now posted a follow-up to his previous post which is also worth reading.)
I should add that I prefer to cook the pork for a lot longer than suggested in both these recipes — I find two-and-a-half to three hours is optimal, to get it really tender. Be careful when stirring it after the first couple of hours, as it has a tendency to fall apart by this point. Another important point is that it's well worth taking the time to blanch the meat before you start, to get out the impurities and make sure your sauce is nice and clear. Put your slab of pork belly in a pan with enough cold water to cover, then bring it up to the boil and let it simmer for a minute or two until the foam/scum has risen on top. Now drain the meat (discard the blanching water) and give it a wash under the tap to remove any remnants of scum. I find this is an easier and less wasteful alternative to skimming the scum off the sauce/stock while the dish is cooking, and I do it as a first step whenever I'm making a stock or sauce from meat or bones.
If you'd like to see 紅燒肉 being made, check out this YouTube demonstration, taken from a Chinese TV channel (all in Chinese, no English translation, but the visuals are easy enough to follow).
An interesting aside on all this is a blog post by Fuchsia Dunlop herself poking gentle fun at attempts to standardise the recipe for 紅燒肉. Also, for anyone wishing to delve further into the intricacies of red-cooking, this eGullet thread on the many meanings of 紅燒 might be of interest.