Wonderful Creative Commons has made it even easier to license your work. In the past, copyright was your only way to protect your work. Now there is Creative Commons which is free and much more flexible. The licenses run the full range from almost total protect under copyright to total permission of Public Domain, and everything in-between. It applies to all types of creative work including audio, video, images, text and educational materials. To get a feel for it, scroll down to see the nifty new Creative Commons banner in my sidebar. Click on it and you can see the license I've placed on this blog.
I love the idea of Creative Commons because I believe the increasingly restrictive copyright laws in the US are stiffling creativity and the movement of ideas. However, I've also watched as generous educators freely shared their work online, only to have it picked up and sold commercially by unscrupulous companies who provide no support to the original author. Creative Commons allows you to prevent that type of abuse, or at least gives you recourse if it occurs.
I also love Creative Commons because it allows me to bring my students to places like Flickr and use Flickr's Creative Commons search section to find images that we absolutely, positively have permission to use, and it makes it easy for us to give the creator credit for their work.
To add a spiffy Creative Commons license and banner to your blog, wiki or other creative work, the Creative Commons website has a really easy to use tool to create your own license. It asks you questions, and then based on your responses creates your license and spits out the code so you can add it to your blog or wiki.
To add the banner and link to your blog or wiki, you do need access to your blog or wiki's code (e.g. In Blogger, I go to my Dashboard and click on the template tab.) Alternately, you can save the banner as a graphic, and just upload it to your blog or wiki and then make that image a link back to the Creative Commons license of your choice on the Creative Commons website. I had to take that route on my WikiPlaces project. All Wetpaint wikis are protected under a Creative Commons license, but I wanted it to be visible on my wiki so I added it that way.
And as long as we are talking about Creative Commons, it is their annual fundraising time. If you are so inspired, you can support them financially. You can also support them by spreading the word. They have this nifty banner on their web site to help you do that.