Code for Open Content
After my post on searching Google for documents that are free to share, Egon asked me about how to indicate that on our sites.
Wikispaces does it automatically and looking at the HTML it looks like you just need to add this tag (or whatever Creative Commons License you choose):
< a rel="license" href="http://www.creativecommons.org/licenses/by-sa/2.5">Creative Commons Attribution Share-Alike 2.5 License >
I've now added this to the template file of most of my blogs on Blogger.