How I Use It
I used Sites to give kids space to document their learning across a number of domains (the standards' domains plus 4 different 21st century skills). Each domain was a page within the site, and each page showed multimedia evidence of their learning in each of those particular domains.
The flexibility worked very well-- kids enjoyed being able to post text, videos, pictures, sounds recordings, and most anything else. The learning curve took some time; kids had to get a Google account, create a site, stumble through some beginner's errors, etc.... allot some time for using these, and become proficient yourself first.
Google Sites are a wonderful multimedia space, but it's important to know that they're only as good as you have a plan to use them. You'll need to play with them first to understand how they work, then consider some ways you can have students make use of their features. The content of the learning experiences you want your students to have comes first; Sites is a great way to give kids flexibility in pulling it all together.