Metadata Wrangler a great plugin by Jeffrey Friedl which allows you to automatically control the metadata which is included (or excluded) from your exported lightroom photos. The plugin works by stripping the metadata from your plugins when you export them from Lightroom. Prior to exporting the images you can specify what data you would like to keep, and what data you would like to exclude. This could particularly be useful for stock / pro photographers who only want to keep the IPTC block (i.e. copyright details and keywords). Once you have set up a preset the same preset will be remembered the next time you do an export, making managing metadata extremely easy.