As you should know, AMD recently moved from Socket 940 to Socket 939, and ExtremeTech have a nice article here, comparing the VIA K8T800 Pro and nVidia nForce3 250Gb chipsets. These new chipsets have a number of interesting features, including the elimination of the registered RAM requirement, which will make for cheaper and faster systems. There's a great series of comparisons of the two chipsets features - one has support for 4 SATA ports and mixed SATA and PATA, which is nice. But you'll have to read the article to see which comes out top!
More here.