Adding a Meta tags CMS function to drupal 7
There is a complete rewrite of the old drupal 6 module nodewords in progress now - it is called metatags. However the metatags module looks like it is still in the initial development phase, so you might be better off using http://drupal.org/project/metatags_quick - which already has a stable 7.x release

There is no releases on the project page, but you could clone the git repo and help with the issue queue and submitting patches back etc