TEDBlog gives us a list of 100 websites they say every one must know and use frequently. I confess I don’t know a great many of them. I will post more when I discover which ones are the gems for me.
Follow-up: I’ve visited several of these sites. None which I did not already know thrilled me. It is worth mentioning the one I knew about that I am not using as much as I should be: scirus.com, where you can search the scientific literature (like on Google Scholar).