I use "English Channel Mats" from Herrington, but they are available under other names from other companies.
Here is a pic:
The deep ribs trap the moisture and slush and there is a high ridge around the outside edge to keep the slop off of your carpets. They come in gray, black and tan now. The material is flexible and doesn't stiffen up in the cold.
They are a little bit more expensive than other brands but the ones I bought have survived Chicago winters since 1990 with little wear!
I currently have WeatherTech (www.weathertech.com) mats in my Eldorado, and they're really great! They look nearly identical to the Herrington mats. I have the Shale (off-white?) interior in my Eldorado, so I ordered the beige-colored mats. The mats are almost a perfect color match to my interior, which is nice considering winter mats usually come in black! They also fit perfectly, with no creasing or bunching.
I always say that I'll only use the rubber mats in the winter, but I usually just leave them in year-round, since they are so easy to clean, and keep so much water out of the carpets. It's one of the best investments you can make!
I also put newspapers over my mats because they are great for absorbing all the saltwater that melts off your shoes. I like the ones in the second post because black is easy to clean or wash, and won't really show stains. I see white mats with a gold emblem somewhere on an add here, and that would not be too practical for our salty conditions, but they would look great in summer.