A few people (myself, Rohit Khare, Assaf Arikin) recently proposed a microformat called hListing that would faciliate this. Microformats are a set of simple open data format standards used to implement structured blogging or web microcontent publishing. Part of the idea behind microformats is to â€œpave cowpathsâ€? â€“ i.e., â€œstandardize and codify emergent, popular behavior on the Web.â€?
You can see their full proposal here.