Oh, man, there is like tons of web sites that use mySQL, infact its one of the most popular databases used for web sites, plus the fact that its free.
Here are a couple examples. One for instance, this web sites www.dbforums.com uses mySQL because I know the forum software they use here, and it only runs on mysql... so everything you see here is driven from php scripts that access a mysql database.
A lot of mom and pop e-commerce web sites run on mysql, because its free. MySQL is also extreamly fast because of its simplistic nature.
You should probably let us know why you are wanting examples for other web sites, it might help in getting feedback, if we know more specificly what you are looking for the answers should be more relevent to what you need.