Great plugin for WordPress. Had a situation recently where a large site we built out on a dev site, had some content with hard-coded links to the development server (dev.sitename.com instead of www.sitename.com). Normally, I’d do a mysqldump of the DB, open the file in vi and do a search and replace. Then import the updated file back into MySQL. Not such a big deal really, but found a much better way.
Search and Replace is a WP plugin that does exactly that. It also gives you the added power and flexibility to choose which tables you want to alter.
Still a good idea to back up the database first, of course.