Having students create a Google Site is an easy way for them to share out what they are learning or creating.  Sometimes you may want to give them a way to get started quickly and even help organize the information for them.  You may also want to use a gadget or have a certain layout for them to use, especially if you want them to use part or all of it as a blog.  For these cases you may want to create a template that your students can use to get started.  They will be able to use the template to start creating their site meaning they will be able to focus on the content and not just the site creation.