One of my new favorite online journals is The Public Domain Review.
From the journal:
The Public Domain Review is a not-for-profit project dedicated to showcasing the most interesting and unusual out-of-copyright works available online.
The journal collects links to public domain works and images from around the web posting them into collections of films, images, texts, audio, and my favorite animated Gifs.
Click on the Sources link and you will see a list of the aggregators of public domain works which are openly available for your use. Some of the aggregators include the Internet Archive, Wikimedia Commons, Flickr: The commons, and The Medical Heritage Library.
You are going to surfing the web anyway, so why not look at some really cool stuff that you can use later on your own article, blog entry, art project, or invitation to your retirement party.