The internet is full of lots of great media such as images, audio files and videos, especially now with the growth of sites that allows sharing of user-generated content (e.g. Flickr, YouTube, Wikipedia). However, just because it is on the internet doesn’t mean you can legally copy and use it in your Blackboard site: in fact most of it can’t be copied. Thankfully there is a growing amount of content where the creators have given permission for others to copy it and use it in different ways. Creative Commons is a popular series of copyright licenses which can be attached to a piece content to specify the ways in which the content can be reused legally. Other content is licensed to the public domain, meaning there are no restrictions on how it can be reused.
To incorporate media into your Blackboard site, what options you have depends on the license for the media. For media where the copyright is unclear or unspecified, you should assume you do not have permissions to duplicate the content on your own site. In this case, you should create an external link to the web page where the content exists (view instructions on how to do this) and let students access it through that web page. With this method you are not copying the content so there is no issue around copyright. Of course, you can use this method for content where you have permission to copy it as well.
Where you have copyright is not an issue, you can copy the media, such as an image, and directly add it into your Blackboard site next to your learning materials (see instructions on how to add images), provided you meet the terms of how that content is used. Items in the public domain can be used without any citations, while most things with a Creative Commons license want you to give credit to the author and the address of the original work. To help with this, Nottingham University has developed an attribution tool (http://www.nottingham.ac.uk/xpert/attribution/) which not only searches across some different sources of Creative Commons content (including Flickr and Wikimedia), but will also give you the correct information to include for attribution purposes. It is particularly useful for images, as it builds the attribution details into the bottom of the image (see the panda picture below for an example). When you use their tool to find relevant images and other media, you can be sure your use is ethically sound and correctly attributed.
If you have content that you created which you want to share with the world, some media sharing sites like Flickr and SlideShare have built-in tools which allow you to specify which licenses you want applied to your work when you are uploading it. You can also use the Creative Commons license picker to determine what is suitable for your work and generate an appropriate license if you are hosting the content on your own website.