if you're already using WordPress 2.3, the Google Sitemaps Plugin < Version 3.0b9 will NOT work for you since it tries to access database tables which don't exist anymore. Please help me getting the new version in a stable state prior the WP 2.3 release.
The current test release is 3.0b11. It works with WordPress 3 and uses MUCH less memory than the older versions. Please test it and report any problems so I can fix them until WP 2.3 comes out.
Here is the download URL to the always most current version:
Thank you very much for your help! :)