Matt Cutts just wrote a post recently on Google adopting NOODP meta tag. It specifies that the SERPs (search result pages) shouldn’t use the description from your Open Directory Project listing (ODP for short, located at dmoz.org). MSN already supports this feature.
Having a listing in the ODP helps tremendously in getting traffic to your site from the directory itself as well as increased traffic from the search engines. If you have a high quality site, I suggest you submit it for approval.
This tag is great though. I hadn’t thought of it, but – what if the editor writes a description of your site that you don’t like? What if your description is several years old? Without this tag and feature, you’d have to be content with the search engines describing your site using the data from the ODP.