To follow up my post on chipset manufacturers, here is a list of websites from workstation providers. These are the sites I was able to find, if you know of others please post in the comments.
Dell - http://www.dell.com/content/topics/global.aspx/solutions/en/vista?c=us&cs=&l=en&s=gen
Gateway - http://www.gateway.com/vista/index.shtml
HP - http://h20219.www2.hp.com/services/cache/305765-0-0-225-121.html
Lenovo - http://www.pc.ibm.com/europe/microsoft/vista/en/index.html?europe&cc=europe
Toshiba - http://www.toshibadirect.com/td/b2c/ebtext.to?page=vista&seg=SMB&location=learn_about
Also, I’ll just post a link, we have GPU sites listed here for Intel, ATI, NVIDIA, S3, and Via.
Enterprise Hardware Guidance