This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
MIME type is a bit more complex. The only place I've seen it used is in the JavaBeans Activation Framework which, given a data source, will use the MIME type to find applications which can handle that data. It's used in the JavaMail framework.