In the last few days, Dan Bricklin posted a proposal for a new XML file format called SMBMeta. SMBMeta is an initiative designed to allow small-medium businesses to include an XML file on their sites that can be aggregated by an internet service to the end of providing a machine-readable/machine-updatable directory of small to medium businesses and the services they offer.
I don't know how far this will go, but I love the idea and hope it takes off. I've already put up my smbmeta.xml file. –)
Also, here's a good intro to SMBMeta.