I'd like to suggest a "homepage description" feature for WordPress SEO by Yoast.
This can really be as simple as supplying a larger text entry field in the "titles" configuration.
If you are using a static page as your home page, the plugin supplies the same description features as any other page or post.
However in the case of the default (twentyten) behavior where recent posts are being shown at the site root, then the plugin only supplies the single line text box where you enter the description template.
Some themes such as Genesis and the Woo Framework allow used to enter a home page description. In the Case of Genesis, the theme hides its own SEO options when a third party plugin is detected.