Look for a hand knotted rug made completely of vegetable dyed wool. Wool is basically indestructible and a vegetable dye is not likely to bleed. Traditional Turkish and Persian rugs for a pattern that won't show dirt (or wine!). As much as I love grass rugs, they are kind of fragile for entries.
Good Luck!

Here's where a better quality rug is ideal--wool originating in very cool climates like Tibet or New Zealand has lots of natural lanolin which repells dirt and stains. If you get cheaper wool, it will never stop "fuzzing" and it will accept stains. Just be sure to take it to be professionally cleaned regularly and you'll be fine. Depending on your climate, such as if you have a few months a year when people will be coming in with snowy boots, for example, you might want a synthetic alternative and save the good rug for the drier seasons...