Don't just duplicate the links that I have on the class web page . It makes it much harder for others to find the truly interesting things you did find if they are buried under a ton of duplication. Besides, I will ignore duplicates when I grade anyway.
Duplication can be reasonable if it is needed for context.
For example, if you are listing a bunch of links about the IETF and you might feel remiss in not having the main link as well. Another time duplication can be reasonable is if you are summarizing or organizing the material in a different way. Don't just put a list of links. You should write a small blurb about what can be found at that link and why it is interesting. At times, it may be sufficient to categorize links and write one description for the hole category.