I use all Shimano components on my bikes (Sora/Tiagra on one, and 105/Ultegra on the other). Typically I just buy whatever they have at one of the millions of LBS's in the city. They usually have bulk cables they sell for like 6, or so, dollars each. I have no idea what they are but they seem to work fine.

They're like guitar strings--some are probably better than others, but if you don't care, and the price is right, they all sound the same.